[Sorry guys, I promise I won't do it again!]
See, what you're saying answers my questions of weather or not whoever took it from Larsen was going to fix what he did or run with it. And the answer is run with it looks like.
There's one reality. A reality that repeatedly undergoes a revision.
Each time a "Revision of Reality" occurs, it's not just that the Supreme is replaced with a new, revised one. It's all reality instantly ceasing to be and getting replaced with a new version.
If you are a person living in a given reality you are going about your day, the Revision happens [reality briefly "flickers", freeze frame, between the current and incoming versions, stopping on the new one] and you wink out of existence none the wiser for ever having existed in the first place.
If you are a person living in the new reality that just popped into existence and replaced that last one, life's going on as usual. You've always existed. Your world and surrounding universe having billions of years of past history, as well as the usual infinite number of potential past / future timelines contained in any other universe, despite only having existing for a brief two-three week period between revisions.
Take that and insert;
If you're Supreme [+ attendant supporting cast / central locales] when the Revision happens, you end up in the Supremacy instead of blinking out of existence.
Up till then you just existed as another of the billions of inhabitants of earth who believed that their world had an entire past history, that you had lived through a childhood and a lifetime - despite only existing for a brief two-three week period between revisions.
Repeat process and you get Supreme after Supreme, along with their relevant pals and places, showing up in The Supremacy.
All very different from each other because each is from an entirely different version of reality. Versions of reality that no longer exist.
Of course outside there always exists a current version of reality, containing a Supreme, forever unaware that they have only existed for a short time so far, and that at any moment they'll all cease to exist [sans Supreme].
That's the rub. Nobody "lives through the change".
The only people left after reality winks out of existence are Supreme and the Lois Lane / Jimmy Olsen, ect. analogues who go to The Supremacy with him.
It's not really a change at all. The Diana Dane who lives in "Reality A" has no inkling of the Diana living in "Reality B". Or of Reality B and the revisions until she arrives at The Supremacy. It's not as if the Ethans, Dianas, and Darius's [not to mention the rest of reality] actually transform from one version into the next; they are completely separate individuals, each new iteration just instantly, physically replacing the last.
The realities are unaware of each other. There's no possible way for someone to know that there's anything other; to them reality is reality and that's the way it is and always has been.
When they instantly cease to exist there's no time to think about it. It's instant. The new people, world, and reality blissfully unaware that they're brand new. As Supreme was when he first arrived at the Supremacy; He had memories stretching back decades but had only existed for a few weeks.
Supreme's world rewrites itself.
It's actually not meta-fiction and metaphor, there's an in-story device and reason, an origin for it.
An original reality existed, in which a set of events occurred, the effect of which set all reality to periodically undergo these revisions.
It had to do with the discovery of the "element" Supremium, a mysterious uber-powerful Kryptonite analogue that is responsible for the creation of the Supreme of this original reality and is the thing in common among the various versions of reality that have come and gone since. Reality revising waves, proceeded by reality altering ripples, radiate from it / the initial event of contact. It's intimate connection with Supreme facilitates his escape from non-existence and deposits him in The Supremacy each Revision.
The reality we call the Extreme Universe, from which the Supreme who was turned into what's referred to as the "Moore Supreme" came from, for some reason had no Supremium. Thus here, instead of a revision happening with none [characters OR reader] the wiser as usually occurs, we [characters and readers] were made aware of the existence of the revisions and The Supremacy solely due to the fact that the Supremium-less Supreme failed to automatically show up in The Supremacy when his reality underwent revision.
The first time such a thing had ever happened.
It's another example of the double-edged genius at work here; we hadn't seen or had mention of Supremium thus far in the Supreme book not only for the real-world reason's of Moore hadn't come along and introduced the concept, but also because it didn't exist in-universe.
It SHOULD have, it "usually" does.
And it's absence caused a malfunction in the revision of the Extreme Universe into the Awesome Universe that replaced it.
Ideally, per above, Revision occurs and reality, in this case the Extreme Universe, ceases to exist [we actually see this happening in-story]. Supreme + related whisked off to The Supremacy with the new reality, in this case the Awesome Universe, complete with it's own Supreme + related, history, and memories, instantly replacing it.
This is how it's always happened since the first reality. All the Supreme's of the Supremacy's realities have disappeared out from under them as they suddenly found themselves in The Supremacy confronted with alternate versions of themselves.
It's not how it happened the time we saw. In fact the very reason we got to see and know any of this is that that's not the way things went this time.
The journey from the Extreme Universe, through The Supremacy, and on into the next, Awesome Universe that we undertook with Supreme was a singular, unique happening. It's the reason we see the Extreme Supreme's memories and history / powers slowly supplanted by the Awesome Supremes'; instead of finding himself suddenly in the Supremacy, his reality erased and replaced by the Awesome Universe and it's Supreme, the Extreme Supreme physically travelled to the Supreme-less Awesome Universe and became, was revised into, it's Supreme.