>So the fairer comparison might be TLS 1.3 under all three, but if you need to upgrade why not upgrade the whole HTTP stack?
Because it's a benchmark of HTTP3 and not a comparison of "as it might be stacks".
It would a bit like bench-marking HTTP/1 with RHEL7 and Apache2, HTTP/2 with RHEL8 and NGINX and HTTP/3 with...let's say Alpine and Caddy...it's just not a clean benchmark if you mix more then one component and try to proof that this single one component is faster.
Especially when their benchmark scenario is something that plays to the strengths of tls1.3 and would probably only mildly be improved (if at all) by http/3
Because it's a benchmark of HTTP3 and not a comparison of "as it might be stacks".
It would a bit like bench-marking HTTP/1 with RHEL7 and Apache2, HTTP/2 with RHEL8 and NGINX and HTTP/3 with...let's say Alpine and Caddy...it's just not a clean benchmark if you mix more then one component and try to proof that this single one component is faster.