mandoc from 2022-10-26 and from 20 minutes ago agree on the following:

Given:
  .de St-p1003.1-2024
  .Tn \%IEEE No Std 1003.1-2024 Pq Dq Tn \%POSIX Ns .1 \\$@
  ..
then
  .St-p1003.1-2024
  .St-p1003.1-2024 ,
  .St-p1003.1-2024 .
all work as expected.
But
  .St-p1003.1-2024 ;
causes -Tlint to produce
  ERROR: incomplete escape sequence: \$\&
  ERROR: argument number is not numeric: \$\&
and formats as
  STANDARDS
       IEEE Std 1003.1-2024 (“POSIX.1”). Fl zqvFs, unit - suffixed. Ar lines
       and. Ar bytes,. Fl - pid,. Fl - max - unchanged - stats,. Fl - retry, and
       more than one. Ar file are extensions, originating_the GNU system. With.
       Fl r,. Fl c is an extension, originating_the. Bx.. Xr sleep 1 Ns - style
       suffixes for. Fl s are extensions.. Fl f is not required^detect
       truncations (and is only strictly required^work for regular files and
&c. The parser is completely exploded. Fl zqvFs and everything forward
is underlined. This is fixed by the next .Sh.

Bookworm mandoc (1.14.6-1+b1) instead -Tlints as
  ERROR: argument number is not numeric: \$\
and formats as
  STANDARDS
       IEEE Std 1003.1-2024 (“POSIX.1 &”). Fl zqvFs, unit - suffixed. Ar lines
       and. Ar bytes,. Fl - pid,. Fl - max - unchanged - stats,. Fl - retry, and
       more than one. Ar file are extensions, originating_the GNU system. With.
       Fl r,. Fl c is an extension, originating_the. Bx.. Xr sleep 1 Ns - style
       suffixes for. Fl s are extensions.. Fl f is not required^detect
&c. The parser is completely exploded. Fl zqvFs and everything forward
is underlined. This is fixed by the next .Sh.

All punctuation works as expected under groff.

Best,