This also doesn't correctly implement HTTP/1.1 (or /1.0). (It doesn't really claim to, either: the README really seems to hint that it is implementing a subset of HTTP that might work in a pinch. I don't think I'd put a production load on that, though.)
The IETF version of QUIC isn't really that bad on layering. HTTP/3 is fully decoupled from the QUIC transport layer, and thereby e.g. stream multiplexing/flow-control is also fully separated from HTTP semantics (unlike in HTTP/2).
Handshake/TLS is also mostly decoupled from QUIC, as are flow controllers (recovery).
Compared to TCP is certainly has multiplexing as part of the main layer, and uses mandatory crypto. But that's more or less the point of QUIC.
Now try HTTP3/QUIC or any of the other "let's just break all layering and abstraction for performance sake" stuff.