This is so misinformed it's funny. CentOS and RHEL will now be down to the compiler flags compatible since RHEL minor releases will now just be point-in-time forks of CentOS with security fixes and backports from, you guessed it, CentOS.
Previously, CentOS was a rebuild of RHEL. In between RHEL releases, CentOS was exactly the same as RHEL. When RHEL had a release/fix/backpoint, CentOS trailed until it was rebuilt from the new RHEL source.
The "old" CentOS was exactly the same nearly always (nearly perfect overlap) and the "new" CentOS is exactly the same nearly never (almost no overlap).
This change makes CentOS so much closer to RHEL that it’s weird that people are acting like the opposite is happening.
If the current RHEL release is 7.x then you can think of CentOS Stream as 7.(x+1). You don't have to worry about it suddenly being 8.0. Fedora plays the role of the future RHEL 8.0.