For many cases you don't even need to make stat() call to determine whether or not the file is a directory (d_type specifically can tell it: https://man7.org/linux/man-pages/man3/readdir.3.html). That's what allows find(1) to be so quick
Well, it definitely does _something_, because on NFS the subsequent stat() calls after reading the directory names do indeed complete instantly :), at least in my testing.
I mean, readdirplus as a local filesystem API. Ultimately unix programs are just invoking getdents() (or equivalent) + stat() (or statx, whatever). Linux nfsclient probably caches the result of readdirplus for subsequent stat.
