> Now it’s still slower by ~0.1s

Not for me. Printing HTTPie's version takes longer than to finish a real http request with xh. I suspect it's because I'm testing it on a relatively old server where the differences are even more pronounced.

[link redacted]

I'm using HTTPie 3.2.1 because Arch doesn't have the latest version available but based on the release notes that shouldn't make a difference.