Do you mean MTLCompilerService after the update? This is definitely related to RAM, I switched 2 slots to 8gb, now it has 24gb. I watched activity monitor immediately after the reboot, MTLCompilerService appeared 7/8 times probably for about 30 seconds each time sometimes overlapping so at one point it was running 3 times. Each instant rapidly increased in RAM consumption then ended just over 13GB. Was over in less than 5 minutes.
No, a bunch of differnet services doing initial setup. I guess Sequoia probably has much more services than older macOS. I guess also spotlight indexing. Anyway, both 12,2 are 8GB RAM and have no RAM usage problems with typical usage. In 5-10 post setup login, its all quiet.