The A'keiyah were the sole healers and physicans of the Island. Since the Island's fall and the loss of the A'keiyah due to the tragedy, any makani who wanted to learn medicine and healing would be breaking the traditional roles. Which, given the amount of time since the fall, it is perfectly reasonable that many makani would have learned the trade by now. But if you are playing a super traditionalist makani, they would likely not follow that route as it is not their place. But if you are playing a makani that is adjusting to life, and trying to be their own person, then it's fine to say they've learned the trade.