Dragon Rage Charmander makes sense as it IS a Dragon, at least as its Egg Group. Same thing with Turtwig learning Withdraw, Totodile learning Bite and Torchic/Piplup learning Peck, while a case could also be made for Chikorita, a Grass-type, after all, getting Poisonpowder, and Squirtle, a turtle, learning Bite.
Of course, it doesn't mean Mijumaru WILL evolve to a Water/Fighting; Qwilfish, Hippowdon, Regigigas and Forretress learn the move for zero flavor reason, and Treecko learns Pursuit also with not much reason. However, I would say this surely increases its chances. From the looks of it, Mijumaru will either become a badass Water/Fighting, or will be an exception.
It doesn't matter in the end because Tsutarja will evolve to a Dragon or Electric pokémon and thus be highly superior, hahah suck it otter