0. emacs -Q
1. M-x man RET cat RET
2. M-: (buffer-name)
=> "*Man cat *"

If you do the same in emacs-29, the result is:
"*Man cat*"

AFAICS this change is due to this commit:

commit 861ac933dd8aed1028edc4b9142400e3702874d5
Author:     Michael Albinus <michael.albinus@gmx.de>
Commit:     Michael Albinus <michael.albinus@gmx.de>
CommitDate: Wed Nov 1 16:54:31 2023 +0100

    Run `man' also on remote systems

If the change was intended, it should be called out in NEWS.  If it was
unintended, this patch restores the previous behavior, at least when
calling man locally (I currently can't test a remote call):