I noticed another setting in the registry that actually works for me in terms of keeping my USB drive awake. It’s
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Power\PowerSettings\0012ee47-9041-4b5d-9b77-535fba8b1442\6738e2c4-e8a5-4a42-b16a-e040e769756e
Make the Attributes value equal to 2 in that key, then set the “Turn off hard disk after” setting in advanced power options to some big number. I tested it at 10 minutes and, sure enough, my external USB drive stayed on for 10 minutes whereas it was going to sleep after 1 minute before.