I agree. Its a bendable "rule" and Apple are willing to bend it in order to make gradual transition. But the Air is also an example that they return to clarity eventually. I don't think they'll continue to sell pros & airs for long if the only real difference is price. I definitely don't think they'll sell Air, Pro & Pro+ for long either, other wise they would have named it something else.

*Not a typo, but I clarified the sentence.