If you use the default parameters with such a implementation you will likely cap out at a pretty slow ~10 Gbps/core, but if you reduce the ACK frequency you can probably get to ~30-50 Gbps/core without too much trouble.
Also I noticed that Plan 9's IL protocol (avoids head of line because the type of messaging it's used for) another point pointed out in the x comments.
I wonder if he's focusing on consumer distributed AI inference (due to quic being browser supported) or maybe just a comment on the protocol in general.