Placing my bets on it being a mistake or flatout lies.

But hoping for real and reproducible

No, you still need display output of some type

It’s not actually available (yet), but why not consider a low profile A380 like this

Relatively cheap, open source drivers, and hardware encoding up to and including AV1.

Edit: oh, and supported on jellyfin. I have mine running on truenas in a fedora 38 VM by passing the GPU through(Truenas scale is running kernel 5.15, so doesn’t have native support).