And as a result putting yourself at a disadvantage compared to the players who have it enabled?
It's not really a disadvantage though. A lot of times, enabled Auto-Reinforce will result in the annoying situation where your manpower disappears by itself even though you are saving for an important new unit. And in that case it's
incredibly fiddly to cancel all the reinforcements & disable AR in time before the mp is gone for good.
I would not use the feature personally unless a lot of manpower is floated in the late game.
What's really broken & stupid however is auto-reinforce on frontline halftracks and ambulances, that shit needs to be removed asap.