if he drained it from the pan first,and then the filter couldn't it cause that issue. wouldn't it drain the filter and the pan, but leave most of it in the engine and lines?
Never in my experience, and I always drain the oil pan first and the filter last. Even if you don't pull the dipstick to vent the oil tank, there is a full time vent line so you won't draw a vacuum. And even if you could pull a vacuum, all you would get is the little bit of oil in the passage between the oil pump and the tank. Only one time did I ever get a little less than a full gusher when I cracked the filter loose, and that was when I pulled the filter on a cold engine that had been sitting for a fairly long period of time. It wasn't empty, however, just 1/2 to 2/3 full instead of full.
I would be very leery of this situation, and not just mention it in passing to the dealer but would insist they check it out thoroughly. Something in the oil cooler adaptor or the oil passages could be wrong from the factory, bypassing the filter.
Jerry