>>717053827
Because a lot of it is already declassified or moved down to a really low level of classification. It's easy to find especially if you are into military gear. There's a lot of books and informational documents that you can buy on amazon or get at a local library near a military base that are declassified but have information in them that is illegal to give out to other countries outside of, like, NATO. Since war thunder forums are worldwide schizos can post something that they shouldn't even if they got it legitimately.
The only one of these that actually turned some heads was when a guy posted specs for a british tank(I think a challenger model) that was either in active development or still being actively used.