Parking spaces are part of the parking. Making them inners of the parking practically excludes them from the parking, so it's wrong. See:

1. "Use amenity=parking_space to map a single parking space on a parking lot."

2. "Note that amenity=parking_space should not be mapped instead of amenity=parking but inside of an amenity=parking."

For these reasons, I'm gonna revert this edit (for the second time).