problem with update-tlmgr-latest.sh on Mac

[Adam R. Maxwell]

A user reports the following error failure when running update-tlmgr-latest.sh via TeX Live Utility:

+ cd /usr/local/texlive/2020/bin
+ tar xf -
./runme.sh: updating /usr/local/texlive/2020/bin/man ...
tar: man: Cannot stat: No such file or directory
tar: Error exit delayed from previous errors.
+ test -r installer/xz/xz.man
+ test -r installer/xz/xz.man.exe
+ test man = win32
pwd
++ pwd
+ echo './runme.sh: no xz.[man][.exe] binary for /usr/local/texlive/2020/bin/man in /var/folders/rq/tmhdm4cx0y91cxcws69tm7z80000gn/T/selfgz190716995/installer/xz.'
./runme.sh: no xz.[man][.exe] binary for /usr/local/texlive/2020/bin/man in /var/folders/rq/tmhdm4cx0y91cxcws69tm7z80000gn/T/selfgz190716995/installer/xz.
+ exit 1

The full log is posted with the report on github,
https://github.com/amaxwell/tlutility/issues/92
but I'm reposting what I think is the relevant part
here per Norbert's request.

thanks,
Adam