Did this change ?, you said, "the passcode you set up for Restrictions long ago is the code you would use for Screen Time."
It used to say something like that on the Screen Time info page but the wording has changed and does not say that any more.
I used to have a Restrictions Pass Code but when it changed to Screen Time I never used it, why, it's useless.
I just tested it and tapped Turn On Screen Time, once on I tapped Use Screen Time Passcode, it said Set a Screen Time Passcode, I said no way in **** and cancelled. Then I turned off Screen Time.
Why did it not ask me for my old pass code ?
Nice to see you are still posting lobsterghost1