I thought the playtest's class-based stat bonuses were clever and interesting, for the reasons previously stated. A cool new idea worth trying. "Fighters are strong." "Wizards are smart." To me, that makes a good complement to "Strong people become Fighters" and "smart people become Wizards." Nature and nurture, working together.
Plenty of real-world examples. Ask a new soldier if he's stronger after Basic Training than he was before. Ask a doctor or lawyer if the demands of their advanced degrees required the development of rigorous new methods of cramming and retaining information. Ask a therapist or practicing clergy if their accreditation required development of new levels of empathy. Of course, yes, serious pursuit of a vocation--serious enough to become a qualified expert--requires training that builds and improves upon natural talent.
But.. should that be in a game? And, different question: should that be in D&D?
Ultimately the answer was "no." I'm okay with it. Easy enough to add in as a mod.