So as I know you have the same rMBP, I bit the bullet and can concur that 14.6b4 is running well on my rMBP 10,1 with no issues during install. A friend who used to code for Apple a long time ago mentioned that very often one of the last few things they tended to fix and optimise in the last few point releases of an OS is power management. Causality and correlation I guess, but this is probably the least of fan spinning I have seen on Sonoma so far. And it used to be quite the issue with constant spinning early on. Ah well. Enjoying the moment while probably jinxing it