I feel a Cameo is a brief appearance of an already established character, like Spider-Man in FF Annual #3; Likely everyone reading the issue for the first time knew who he was. Wolverine was in just one panel of 180, but the reader didn't know who he was because he'd never appeared in a story before this issue, making it a first appearance- Any description other than "first" is irrelevant IMO
Some are very lame, like Darkseid, and if Forever People becomes the book to have because it's a better appearance, then that's that- But it doesn't change that Darkseid appeared in JO134 first.
Sometimes it seems the problem is people feel that admitting Hulk 180 and others like it as being the 1st appearance means the value of their 181 (and others) will drop. Why would it when placing the higher value on a 1st app is not a rule that we must follow? And if one day covers become less important than context, causing 180 to become the book to have, so be it- The Market will have decided, but only to the value because that's all the Market can decide.
That's how I see it, fwiw