Did Marvel UK have editorial jurisdiction to force Marvel US to consider their books as part of the continuity of the US books? No, of course not. However, did the US books consider them part of the continuity? Yes, without question. Before the Thorpe/Davis and Moore/Davis run you had Captain Britain turn up in Marvel Team-Up and had his origin and history from the UK comic confirmed as part of the US continuity. When Captain Britain next appeared in a UK title, a story where he co-starred with the Black Knight, his appearance followed on directly from that US appearance, referencing his flight home over the Atlantic. Just as the Moore run was getting underway, Marvel US acknowledged the Black Knight/Captain Britain story was being confirmed as part of US continuity by dint of the Knight turning up in Avengers in the same costume and with the same steed that he had previously only had in the UK story. The UK stories have always been part of the overal
You make it sound like they were some licensee. They weren't. They were another branch of Marvel. There had been licensees for Marvel in the UK prior to Marvel UK being set up, but Marvel eventually decided the market was too lucrative to just let someone else reprint Marvel's stories.
Sneaked in? You make it sound like he cunningly tried to hide it from the bosses. Hardly. He probably was the first to use the term in a US title, but it has been used multiple times by other creators.
They might not have liked it, but it was official. It got used too many times by too many writers to be considered as just some "fan thing" by anyone who isn't blinded by an irrational dislike of the terminology. Heck, it was so official that when Marvel decided to celebrate Captain America's 70th Anniversary, which issue did they do it with? Captain America #616. If they'd wanted to celebrate it exactly 70 years after the first Captain America appearance, then they should have done the celebration in the March 2011 issue, which was 614, but instead they delayed the celebration issue to 616. That's not coincidence.
I have read the whole article, and it is clear that Alan Moore and Alan Davis have different recollections as to who came up with the term. Given the evidence, I have little doubt Moore is the one recalling things correctly.