Why lie about this? The person who published this document (gulagu.net admin, coincidentally the site has been down since then) is well known and widely thought to be a reliable source.
FWIW it has at least passed a sniff-test from Bellingcat, which is probably as close as us normal mortals will ever come to being able to vet a doc like this. If Bellingcat FSB sources suggest this was 'probably written by a colleague' then it at least moves from /r/warcollege fanfic and into the realm of potentially legit.
It wasn’t “found on the internet”.