Forgive me if my response seems convoluted.
To get an accurate comparison of results between cloning and using RoboCopy, I decided to use the original souurce and original target USB sticks.
At the time that I made my previous post, I had tried to do this 'experiment' in a separate PC (with a 64bit version of Win10ProV20H2), kept specifically for trialing purposes. In that PC, the source USB showed as D. Then I asked you whether leaving it as D would work, since you have an 'XD' term in the code.
Having found Robocopy.exe (2019) in \Windows\ in the PC I am writing you from (32bit Win10ProV20H2), I expected to find that in the 64bit PC as well - but NO, all it had, was the EasyRobocopy I recently installed, because 'you' had recommended RoboCopy to me; so I figured that I could not expect the batch file to work there.
So instead, I tried the batch file in a clone of this 32bit system. The source USB already has the drive letter U allocated, so I kept that ,and designated the target as V and altered the code to say "robocopy U:\ V:\ /U /Z /XD "System Volume Information" /R:5 /W:5 /PURGE"
On running it, the first attempt mentioned an error #3 : U.
I found that I had made a mistake in the REM, leaving 'F' instead of replacing it with 'V' - so I corrected that. As far as I know, whatever follows REM has NO influence on the running of a batch file. I ran the batch again, and there was NO visible reaction.