It seems you need to urgently reach out to the people working on WebTransport. You seem to know better and their documentation contradicts and refutes your assertion.
Where does that document say that WebTransport is just WebSockets over HTTP/3? The only thing in common is that both features provide reliable bi-directional streams, but WebTransport also supports unreliable streams and a bunch of other things. Please read the docs. There is also RFC 9220
Bootstrapping WebSockets with HTTP/3, which is literally WebSockets over HTTP/3.
Maybe? Isn't WebSockets basically TCP? Roughly? I wrote that WebSockets provide reliable bi-directional streams, but it actually doesn't. It implements message framing. WebTransport also doesn't support "unreliable streams", it's actually called "datagrams". WebTransport doesn't even have to be used over HTTP/3 per the latest spec, so is it basically WebSockets reimplemented in HTTP/3? No.
> (...) but WebTransport also supports unreliable streams and a bunch of other things.
If you take some time to learn about WebTransport, you will eventually notice that if you remove HTTP/3 from if you remove each and every single feature that WebTransport touts as changes/improvements over WebSockets.
No need for WebSockets there as well. Check out WebTransport.