Makeinfo versions < 6.7 detected mistakes in the @menu structure of TeXinfo
input. Makeinfo versions ≥ 6.8 don't do this any more by default. They need
an extra option, for this validation to happen. See
<https://lists.gnu.org/archive/html/bug-texinfo/2023-06/msg00015.html>.

Since doc/coreutils.texi has a hand-written @menu, it should use this extra
option.

Here's a patch to that effect. I checked it by running
  touch doc/coreutils.texi; make doc/coreutils.info V=1
and
  make sc_makefile_at_at_check