Like I said, I don't have easy to access links to their posts, but you can try doing a search of their usernames and certain designations to see if anything pops up, or even make an account for the relevant forums that they sometimes inhabit. Unfortunately, sometimes their posts are deliberately cryptic, so personal interpretations of what they mean are kind of important.
However, I can confirm that those designations (001A and 002) have been used by the likes of fzgfzy and pop3 directly, I do have memory of that. (for example, here's one post among many by fzgfzy where he directly uses the 002 designation:
)
As for 001A and 002 possibly being their "stand-ins" -- well yes, that's kind of what I've been trying to say.
No one here is saying that 001A and 002 are necessarily official PLA designations of the carrier projects (we don't have proof of that, after all), however those designations (through whatever reason) over the years, have ended up becoming the generally accepted designations for the carriers and certain consistent characteristics have been assigned to those designations over the many years of continuous rumour and big shrimp cycles.
And for better or worse that's just what everyone in the community calls them now, and we take after the Chinese language PLA watching forums. You could try challenging their reasoning over there directly, because doing so here, the best answer we can give is a shrug and to basically restate what I've already said.
As for their "big shrimp status"... that's derived from their own prediction history and their general regarded status among the boards, and I think fzgfzy is also a contributer to a semi-official naval magazine. Some of them just know things that other people don't and predict things with disturbing accuracy.
That doesn't mean everyone takes each of their words as gospel, but it does mean whenever they say something people do take notice, and people can make draw their own conclusions based off patterns and other evidence, and that's a good enough methodology for me.