I think you might want to go back and read his post here describing what happened. He was on flat ground, not using his tractor when it happened.
More on leaking axle seals and vents - TractorByNet.com
It's not a simplification, the only way oil can come out the vent is if the vent tube is submerged in the oil. Period. I can come out if it is surrounded by air.
Again, if you're interested go back and read my analysis of how this happens and conditions that can cause it. (Driving on an incline with a cool axle that heats up
might do it but my theory is that the oil is moving around enough in the case to allow air to pass the vent keeping the axle and outside temp equal.)
As I said before two things must be present:
1.The vent must be below the oil line
2.There must be pressure in the case.
Parking on an angle, by itself, won't do it without pressure in the axle so if I'm using my tractor and I park it on a hill with the tranny hot it isn't going to push oil out the vent, if anything it's going to draw air in. If I'm parked on a hill and start my tractor and let it sit there the tranny won't get hot either because there's no friction in the case from moving to heat it up and thus no pressure.
I don't expect to have problems with my vent, if I do I'll report it here. I used it extensively yesterday in all kinds of positions, so far so good.
Rob