There is ABI parity, though. If it were any other way, RHEL couldn't be "a point in time snapshot of CentOS Stream" and still maintain a stable ABI.
The only place where it gets a little bit fuzzy are kernel modules.
The only place where it gets a little bit fuzzy are kernel modules.
So unless you know the exact timestamp that RHEL cut their release from CentOS Stream you no longer have the guarantee that it matches RHEL.
Whereas before CentOS WAS an exact copy of RHEL and if I compiled a binary on CentOS 8 it would work without issues on RHEL 8.