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So I tried to breed Jangmo-o with Shell Smash but unfortunately it didn't learn Shell Smash. :(
Maybe there's an item to be held for it to learn SS or it is indeed an error.
Okay so I managed to get its moveset through mock battle.
Kommo-o
Item:White Herb
-Shell Smash
-Outrage
-Sky Uppercut
-Poison Jab
I doubt this is an error. Maybe there is another way getting this move.
I battled someone in the Battle Tree with a Kommo-o and was surprised it used Shell Smash.
I looked in its learnset but it wasn't listed there.
This changes everything!