For the record, these are not the same things. “Orphan” has 2 different meanings, which is on display here.
lib32-audit is an orphaned AUR package, meaning that it has no dedicated maintainer to keep the package updated from upstream.
But when pacman searches for orphaned packages on your system, what it is showing is packages that were originally installed as a dependency of another package, but that dependency no longer exists (because the originating package was removed or it no longer requires that specific dependency any more).
These are 2 very different types of orphan. So pacman -Qdtq will not find that an installed AUR package no longer has a maintainer. Yay, however, will report that during an AUR update.