Two users can't simultaneously be using two separate versions of Perl

Sure they can.

Screenshot of Task Manager showing two different users running two different versions of Perl

This is due to how PATH env var works on Windows.

If anything, Windows is more flexible than unix systems.

The real difference is the lack of cmd startup script and lack of cmd functions.

PowerShell might have those? If so, you could have a true perlbrew for PowerShell.