Gregory's ServerNo, it's not crossposting to Mastodon, it's federating.
If you reply to a tilvids post in Mastodon, that reply appears as a comment in Tilvids, because it's the same post.
Tilvids is trying to create a good well-moderated server where established video makers can publish on the Fediverse without being posted alongside conspiracy theory videos etc.
The admin has been patiently negotiating to get more good video makers onto the Fedi, and I think they deserve support for that.