There’s a LOT of oil left in an engine after draining. I rolled a set of main bearings into a C13 Cat that sat in my shop with the oil pan off for a week and it still had plenty of oil coming out when the main caps were pulled. Whatever small amout of oil may be held in the pan by a Fumoto drain plug is nothing compared the what’s in the oil galleries, bearings, oil cooler, recesses on the cylinder head, etc. You are worrying about nothing. Fumoto drain plugs are the best in my opinion. I have one on all my vehicles. Helps to prevent problems with drain plug threads, too.