It's annoying indeed, not only can you not do any software that has any amount of graphics, but there is no word from any Microsoft Operator and it's been nearly a week after they've launched their firmware. This is the SECOND time their firmware update has caused the internal fans of the Surface Book2 to pop into LOUD or HYPER mode when they never did before.
If any want to TEMPORARILY Fix your loud Fan problem on your surface book 2 you are experiencing since April's firmware update from Microsoft, restore a recovery point before it was loaded and make sure that Windows can't auto-update turn that setting off.
Don't do anything drastic and go wiping out past firmware updates by deleting them, mess with your voltages or registry. I deleted the firmware updates the first time through rather than recovery, held off the firmware update as long as WINDOWS would allow me and it ended up blue screening my SB2 making it not even operate and forced a lot of unnecessary work. This is done from the update, wait and hope Microsoft doesn't hold the remedy out for too long.