Inconsistency between egg moves for some pokemon

Azumarill has some move that he should learn but dosen't (belly drum and aqua jet are the only one i found).
Azumarill is in the list of pokemon that can learn belly drum.
But when i go see the moves he can learn, belly drum is not in the list (it should).
It's the same thing with aqua jet.
At first i thought that it was a problem with egg moves in general but i didn't found any other pokemon that have that problem.

Steps to Reproduce:

1. Search the pokemon "Azumarill" on the api
2. Go to the moves section -> "Azumarill" can't learn "belly drum" (wrong)
3. Search the move "belly drum" on the api
4. Go to the "learned_by_pokemon" section -> "Azumarill" can learn "belly drum" (correct)
   The steps can also be done with the move aqua jet

Azumarill should have belly drum and aqua jet in the list of the move he can learn.

EDITS :
After more research i realised that it's a problem with a lot of other mon that should learn an egg move but don't
the pokemon that have the same problem :
-slowking and slowbro with belly drum
-ursaring and ursaking with belly drum
-clefable with aromaterapy

All of those pokemon are evolved version of a pokemon that learns the move only with breeding.
The move need's to never have been a TM.

There is probably a lot more inconsistency like that but those are the only one i found yet

Start by reproducing the Azumarill responses for the Pokémon moves list and the move endpoint's learned_by_pokemon list, then compare the same data for the other listed Pokémon and moves. Trace where the egg-move data for these API sections comes from; done means the affected Pokémon and moves appear consistently in both responses.