Wishiwashi dive

[guidy]

I was able to catch a Wishiwashi in Reborn and wanted it to learn Dive. It normally learns Dive by the level of 30, but it was way over that level so it didn't know that move anymore.
Luckily I was already able to obtain the TMX for Dive and wanted Wishiwashi to learn it by TM, only to discover that it could not.
I noticed at the move relearner that I can relearn Wishiwashi the Dive move, so here I am wondering why the TMX won't let me.
Now, I do know that dive wasn't a TM in Sun/Moon so that officially Wishiwashi can't learn Dive by TM because it wasn't a TM in the game.
But in this game Dive is a TMX, so wouldn't it make more sense that it can learn dive through TMX, because it already learns Dive through leveling up?

 

(Sorry if this has been pointed out before, I could not find any records of it however)
 

[Faeborn]

S&M stuff is still pretty new and there's no dive tm in those games, so it may very well be an oversight.