SSH is actually really slow on high latency high bandwidth links (this is what HPN-SSH patches fix: https://www.psc.edu/hpn-ssh-home/hpn-ssh-faq). It's very apparent if you try running rsync between two datacenters on different contients.
HTTP/3 (and hopefully this project) does not have this problem.
Sounds like a complex change to fix a security protocol but, reading the page, it seems to just increase the send buffer, which indeed makes sense for high-latency links