Chrysler starter spin down time

Ok,I just swapped out the starter with another one. This one has a "professionally rebuilt by Autolite" sticker on it,where the other only had a "remanufactured in Mexico" label. The both act pretty much the same,but the autolite one seems slightly quieter on the spin down. so looks like they are all like this.
One thing I did notice is that the armature housing on this one has a small hole in it where the other didn't. Can any of the Mopar experts out there tell me what this hole is for and if this is supposed to be there? I would think they would want to keep any road dust and dirt from entering there.
I have attached a photo.