CentOS Stream 9 is the next minor release of RHEL.
Thus installing RHEL 9 packages on CentOS Stream 9 is technically equivalent to installing RHEL 9.5 packages on RHEL 9.6. So most of the time it is safe.
You should not have a need for that though. CentOS Stream 9 contains all the packages from the released RHEL 9 repositories with the exactly the same ot a higher version.
Well, the CentOS machine has no internet connection, only a local network. We do have the on our local network RHEL 9 package mirrors, so these I use to install things on tge CentOS machine.