Answer 1

It is because of the fact that Meteor Mash is a Punching Move, so it is logical to add it in the list. This may symbolize that a Pokemon in Gen VI might get that combo, but that is not yet known.

Comments

Also note that a Pokemon in a later generation might have this combo.

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Also allot of people hack illegals sets

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Or play in Hackmons on Showdown! :P

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some skill swap and metronome/meteor mash combo could be possible. also, hitmonchan if his ability can change upon migration