[SnailsFromJupiter]

The final response on my StackOverflow question relating to this issue was:

Unfortunately, I’m still not sure what that check is actually there
for. $post should be an object during the_title filter, no matter if a
post is returned or a 404 is shown (so is_object( $post ) seems
redundant)…$wp_query should be NULL if you’re on a 404 page, since
there’s no actual query object. Otherwise, I have no idea when
$wp_query->post->ID wouldn’t be equal to the $id passed to the filter.
Honestly, I’d remove that check in favor of using if (
!get_queried_object() ) return $title;