Now that I know that the dipstick is much larger than on mine, it could take much less pressure to blow it out.
As far as I know, about the most replacement flow you can generate is if you had all the cylinder rods extended, and then you retracted them all as quickly as possible. This would be like if you had the bucket all the way up, and the bucket curled, and then you simultaineously lowered the bucket, and curled the bucket back up at the same time. You could even involve the 3pt in this game (Lift is up, and lowered at the same time the FEL boom is dropped, for example.)
If I am right, the oil level in the sump has to rise the amount of the volume of the cylinder rods (but for the 3pt, which will be the entire bore volume .) That is not an inconsiderable amount of air displacement.
Maybe a test: Raise the bucket fully, perhaps with a little weight in it. Pull the dipstick to relieve any air pressure/vacuum. Put the stick back in, and then lower quickly. (could put a little bubble water on the vent before the lower.)
If the stick stays in, pull it out, and see if it comes out with a pressure assist.
If it doesn't come out on its own, and if when you pull it out, you do not hear a pop, or the stick does not come out extra easy due to pressure, then so far as I know, the vent is serving its purpose.
