Latest SteamVR driver includes this in its update notes:
Fix for application performance activating ASW
And... it absolutely works. The stuttering introduced in the December Oculus update has been a major and vocal problem for alot of people. After 6 months of smooth playback, I haven't been able to use my Rift S at all in either Oculus' software or in Steam without horrible stuttering. We have all known its related to ASW but Oculus has done nothing to address it. Now Steam releases this fix and I can use my Rift again for the first time in 4.5 months, but ONLY in Steam. Everything is still completely broken through Oculus' software. That blows my mind that I can only use Oculus' hardware in someone else's software. It also blows my mind that Valve/Steam stepped up and fixed a rival's headset performance for them that Oculus themselves won't even bother with.
I can now fire up a complex game like Half-Life Alyx in Steam (which stuttered horribly before this update) and now it plays perfectly. But if I simply open up Oculus Home its a stuttering mess. I sincerely hope that this is horribly embarrassing for Oculus and that it lights a fire under them to fix this issue.
In the meantime I cannot see any reason in the world why anyone would buy games through Oculus instead of Steam.