First thought is that when you transfer to shoes with cleats, they’re more likely to have an inflexible sole, so you’ll get better power transfer. I don’t know what shoes you’re using now, but if they flex, then yes, it will load the pressure just onto the area that meets the pedal rather than spreading it around the whole of the foot.
Second thought is that if your heel is in danger of dropping on the downstroke, your saddle height might be too low?