I saw that as well.
However asdf.sh is not there:
ls ${HOME}/.asdf/
installs/ plugins/ repository/ shims/ tmp/
I did try creating a link
ln -s /usr/local/opt/asdf/asdf.sh asdf.sh
But failed miserably because the script points to directories relative to the original asdf.sh
I have asdf’s lastest version. And, BTW, this started happening to me in a newly migrated Mac (now) using Big Sur
