The «air» is here an allegory for «large language corpus». It is self-evidently true that as we move backwards through history we eventually pass the first language utterance for any given definition of language or utterance. From here on out, the «air» is indeed «thin». There are still other things, but no «air» (i.e. «language corpora»).

We either have the capacity to make boats and traverse the oceans or we don’t. These days almost nobody makes boats, but we sure used to and still can. What’s your point?

Whatever semantic game you want to play here isn't relevant; the point is it's something humans can do that AIs cannot.