Glad this worked for you. Certainly simpler than my protocol. But, consistent with the root cause of the problem.
You can leave RST installed and rename iaStorA.sys so it is invisible when Windows update checks for it because the more recent versions of RST use iaStorAC.sys as the driver for the SATA.
What I was not sure of is whether Windows update would block installation if RST was installed and there was no iaStorA.sys file for it to assess the version of RST.
I wholeheartedly agree that someone should have tested the "fix" and realized that updating RST did not update the iaStorA.sys file. It is especially absurd to since the 1903 build reinstalls the same iaStorA.sys file during the update.