> As you note, our models are ordered: Luna < Terra < Sol < Astra

That is false, considering Astra and Luna don't even exist for 6.1. Terra didn't exist for 6.1 until yesterday. You don't get to make up imaginary tiers. The inconsistency wrt their availability, starting with day 1 of a new model version, is precisely the problem. OpenAI is a user-hostile joke of a firm that users would do well to abandon.