Your question spurred me to look through my engine manuals to see if this is addressed. I did not find anything. I know installing engines, there is usually a fore/aft tilt that the manufacturer typically specifies.
Marine engines must be able to handle a certain amount of heal, but your point is well taken. I know I've watched/helped pull boats through areas (usually deep draft boats going into entrances with a shoal that has to be passed over) where the sail boat was running it's engine while being both towed from the front and being healed over by a boat on the side attached to the mast head. Was that good or bad? I don't know for certain. No one ever complained...
dj