Okay, hopefully I got better at explaining myself during these past 4 years.
I'm going to use Farfetch'd because Vullaby is a bad example. In generation 5, Farfetch'd can know roost as an egg move. So if I bred a female Farfetch'd with a male Chatot that knew roost, then the eggs would be Farfetch'ds that know roost, right?
If roost was a TM move for Farfetch'd, instead of an egg move, then Farfetch'd should still be able to inherit roost from any father that knows roost. So if I bred a female Farfetch'd and a male Chatot, then the children will know roost as long as the father knows roost. The father could have learned roost by level up, TM, or even passed down from its father. IT DOES NOT MATTER. The children will know roost.
In general, any move that is on a TM can be passed down the same way as egg moves. It doesn't matter whether the father actually used the TM to learn the move.
So listing a move as an egg move has no in-game effect if it's already a TM move.