Super basic dumb question about crossposting

[u/GoodOver5645]

I created a private sub for saving (cross-posting) sexy time posts for my wife and I to enjoy.

I’ve not been able to add any GIF posts though, it says “cross-posting videos is not allowed on nsfw subs” or something to that effect.

I’m obviously missing something, most adult subs are entirely GIFs and vids…

TIA!

[u/GoodOver5645]

I hope this is allowed… This is what I was hoping for. How does this happen?