My goal is to set up permissions on a user account profile to be readable by another user. I'm setting up such scheme for an automated backup purpose.

So, say I have two standard user accounts -- User A that is a general user of the system, whose data will be backed up:

And BackupUser that will be doing the backing up:

I want to set up permissions on the User A's profile folder C:\Users\User A to be readable by BackupUser.

So I start a cmd as administrator and run the following icacls command:
icacls "C:\Users\User A" /t /c /l /q /grant DESKTOP-69AQNQQ\BackupUser:(RX)
But it fails with errors of access denied to some folders.

OK. So I downloaded PSEXEC and first run my cmd as SYSTEM hoping to prevent access denied errors:
PSEXEC -i -s -d CMD
and then run the same command from it. But it still gives me the same errors:

So as a result when I try to copy the C:\Users\User A folder from a process running under BackupUser user account it fails with, you guessed it, "access denied" error.

So what am I doing wrong here?

PS. I'm doing these tests on Windows 10 Pro.