I have two large OE's, a generator and a snowblower. Both have instructions on checking the oil levels which state that the dipstick is to be set on top of the oil fill hole; not screwed in or pushed down past the o-ring on the lipstick.
This is a $1900 engine so I would reread the manual to determine the proper procedure for determining the oil level.
I did after I posted not seeing your comment at first and thanks but yes, if the lipstick is to be pushed all the way down, then a quart of oil is not being drained.
How are you "draining" the oil, with the drain plug or sucking it out of the oil filler or dip stick hole? If you're sucking it out that maybe why it can't pickup all the oil in the sump.