Slightly academic question I know. But everyone in comics is so obsessed with decompression it occurred to me Spenecr isn't really using it. You may think, "Hang on a minute he took months to tell his story about Captain America" but bear with me.
Decompression is usually seen as opening up the story and spinning it out over many issues, such that the actual events are few and far between. This is usually contrasted with older comics that seem to have lots of incident happening in a single issue. I am not saying Spencer is doing the latter, but I have always had an issue with this idea because it depends how you define incident. Take for example an often quoted addage by Henry James in literary circles: “What is character but the determination of incident? What is incident but the illustration of character?” (You can tell he was a writer and not a critic, he has a lovely turn of phrase.) In this simple truism James is pointing out the interconnected nature of plot and character. What many consider decompression is actually an emphasis on character, and when you strip that idea down to its basics then much of the incident in a modem story is not action but character focused.
I always think that the way to tell if a story is truely decompressed you need to try and summarise it. If you can do that very quickly and convey everything significant that has happened then we may indeed be looking at decompression. If you just relay the action and ignore the character beats you are cheating. A truely decompressed story has very few combined action incidents and character incidents.
Related to this is how tightly plotted a story is. In a tightly plotted story everything that happens is important to the story. Very few events happen that are incidental or insignificant to the story. It is fair to say a story is decompressed if a large portion of the incidents are not actually particularly relevant. Indeed when many people criticise decompression this is a big factor. Some readers may consider references to two characters' old and almost forgotten relationship to be vital to the story, because they have always valued that relationship. A book that shouts out that Storm and Forge have a complex past together will contain an incident that divides the audience. Some will count it as a vital one, some will pass over it looking for something they care about because it really isn't impacting the plot.
So look at Spencer's Captain America stories. Although they plodded along at the normal slow pace of modern comic books, by the time we got to Secret Empire #0 we can see that barely a panel was wasted on unimportant points. The whole run was very tightly plotted and full of incident that proved relevant to the story.
While not significantly changing the overall pace of the books, and therefore not going back to an earlier age of comics, Spencer is significantly increasing the relevance of his incidents, leading to a tightly plotted and retrospectively heavily laden with significance. All the character and action incidents are relevant, even if they felt incidental at the time. The trick, tightly plot your story, lay lots of pipe, pick up dangling threads and try and tie things together at the end.
To be honest this isn't a new trick. Dickens was doing this in the very early days of serial fiction. We could all name some comic writers that have done this too. Just see a list of classic comic runs. It could be argued Hickman was also doing this, but he seemed to get a little too busy to really tie up everything. Let's hope Spencer can keep his schedule under control.