Your goldilocks theory is one I am sure many have pondered, and I am inclined to say is correct. That would also support why the correct application of acids works better: the seed coat is weakened all around the seed, rather than just one spot.
The budding horticulturist in you is very encouraging, and your willingness to consider multiple avenues of understanding is a prerequisite. Many great plantsmen have their major careers in other genre; perhaps you will someday be one of them(!)
