On Jail Break(TF2) the rules never say anything about healing as a medic counting as afm so it usually is decided by warden. In advanced options there is a setting where your medigun heals without holding it down so it would be considered afm. The common counter argument is how do you tell if its afm or not? That is true so I personally think it should be a rule since you can't tell if a medics healing is afm or not. That if the Medic stops healing or switches targets it's considered not afm since they are using their mouse to switch.