Are you using the RestictEvents.kext? Maybe using that kext might help.
Also here are methods used to change the CPU name in About this Mac (other than with the RestrictEvents.kext), which I am sure could be adapted to do the same for your memory speed, if you really want to go that far.
IIRC, you would need to disable SIP and reset Nvram, AppleSystemInfo.framework needs to be copied to the desktop before it can be edited, a new snapshot of the Monterey/Big Sur drive has to be created which includes the edited framework, you then need to make sure you boot from the new snapshot.
This to me sounded like a lot of faffing for not a lot of gain, and what gain there is only being cosmetic in nature. But in case you really want to do this here is a thread that helped someone rename their CPU -
https://forum.amd-osx.com/index.php?threads/processor-unknown.1389/