Mercedes has been using topside oil filters for a few years and most of their new engine are designed for its use with the drain plug added as an after touch. Merc dealers even use top side.
Also, note that drain plugs in engines do not always drain at the very bottom of the oil pan, there is usually a lip at the bottom of the oil pan where grease and oil can sit. On the other hand, top side is usually drained out though the dip stick with the drain hose feeding to the bottom. Dip sticks go to the very bottom of the oil pan and the top side is strong enough to suck up grease and junk.
From what i have read, topside removes all the old oil in engines and transmissions. any leftover(if any) wont be an issue for the oil filter just like in an oil change using a drain plug.