After the Aug 11 updates (2nd Tuesday monthly), the MoUsoCoreWorker.exe process is no longer showing up under powercfg /requests. And, if I put my computer into Sleep mode, it stays that way. But, it still will not GO to sleep after xx minutes idle. I just tried the KB4568831 fix, but I get a message: This update is not applicable to your computer.
Update - Aug 18, 2020
I discovered that when I unplug all USB A/V devices, the computer goes to sleep as expected. With those devices plugged in, powercfg /requests always shows their drivers as active. This is new behaviour which began with Feature Update 2004.
I tried (as someone in this thread suggested) powercfg /override, but that did not work for me. I have to physically unplug the USB devices - really annoying.