Looking at them isolated, I think the restrictions for MM are good. Without these restrictions, MM would be extremly strong and no mage could skip it ever. So in itself thats a good design
The problem arises when comparing it to MA, thats when MM starts to look like pure shit. Because MA does not have these restrictions while doing more damage at a longer range. MA can easily cheese every pve encounter, MA is so good that its mandatory for every character that can use a bow ( so everyone except mages) its so good that no mage can hope to ever win against MA, no matter if he is mounted or not.
This difference in power just does not make sense. So there are two options:
1. Decide that mounts are mandatory and should rule everything, then MM has to be brought up to to the level of MA. In that canse the MM restrictions must go away
2. Decide mounted styles should not dominate everything, then MM is fine and instead MA has to be brought down to the level of MM, which probably means reducing the damage and also not allow them to turn.