yeah tags/kw and why they doing it idk but im sure there's some kind hided reasons mostly they use embedded code or api to publish those videos which means no seo much in there but when they publish your description and URL in there that's straight do-follow juice right there I can't much tell how u can check this and if is passes barriers but if you know at lease basic knowledge of how seo works u might be all figure out this on your own by manually reviewing small thinks they do to your videos in other words testes testes testes and by the end of the week you be more knowing wtf is going on
about your PM the free domains I offer to guy because he started journey and took time writhing it, unlike you just asking for same thing out of the air kind a got to deserve it i mean this in most nicest way possible don't take too personal
hope that's answers your questions and good luck