Why is the glibc flavor needed?

[rdbisme]

Hello. It's "the Season", and I'm trying to keep myself entertained with fundamental questions.

The question of today is: why a curl-linux-x86_64-glibc is needed? At first, I thought that in case of glibc, it was not statically linked with glibc but only dynamically linked (on a old system to provide binary compatibility) to avoid the NSS problem mentioned in the README (btw this is what ChatGPT told me... :/)

But it seems that indeed glibc is statically linked into the binary.

Then why it is? Wouldn't the musl variant cover also glibc based systems without the NSS problem? Performance reasons?