Because these new PCV systems really suck, literally, at idle, draw about 19"/Hg of vacuum at engine idle.
The source of this vacuum is where the PCV hose goes into the inlet of the turbo, is a venturi, air from the air cleaner flies over this to create this vacuum. Leaks can be in the camshaft cover, PCV hose, oil filler cap, or the dipstick itself, also has a pressure switch, manual does not say when this trips, guessing around 4"/Hg, if it drops below this point, will set a Type A code, CEL will come on, only way to reset it is with a scanner.
You can't check your engine oil while its running anyway, pumping oil all over the place, will always read low. When I change my engine oil, only add four quarts, take it off the ramps, start the engine to take it off the ramps, and pray the oil light goes off. On level ground, wait about five minutes for the oil to settle,then check it, then fill it to the full mark on the dipstick. Do not want to over fill it, more problems. Always check the engine oil and coolant when cold, both should be at the full mark.
All this stuff is basic, but those kids working at the dealership don't even know all this stuff. But like to call themselves the experts.