Scientific clusters have more options though, as Rocky/Alma and other alternatives to RHEL are available without dealing with "this distro does not ship FIPS-140-3 certified crypto" or similar.
Yes, that's true. However, tons of software was written solely for CentOS, so ironing out the small kinks will take some time.
The problem is, scientific software can silently error out in many ways (like slightly lost accuracy), and detecting and fixing those will take some time.
Considering some of these tools are developed over (almost two) decades, there's a lot of verification we have to go through.
Considering how many interesting issues that specific CentOS7-locked job had just with updating kernel to latest LTS (which required a lot of fun stuff as well, given that it didn't compile with included GCC)...
Rocky and Alma are okay-ish for scientific clusters. They work and drivers appear to mostly cooperate. Some changes, like switching to sssd, were suboptimal but to be expected.
CentOS just had a lot more testing being done by vendors. We still regularly hit problems with, e.g., Lenovo LESI being not aligned with our Rocky systems for many parameters.
Anecdotally, I am hearing scientific computing customers who are unhappy after moving to Rocky - the window where each minor OS version is "supported" is too small and their hardware vendors have trouble staying current. Have seen quite a few move to Ubuntu, and the rest switch to regular RHEL.
The problem is, scientific software can silently error out in many ways (like slightly lost accuracy), and detecting and fixing those will take some time.
Considering some of these tools are developed over (almost two) decades, there's a lot of verification we have to go through.