The implicit assumption is that these AI-company jobs were recently created and indicate the start of a trend.

Chalmers is stating that there's more demand for philosophers with the right sort of training to work at AI companies (whatever that is) than there are philosophers with that training. (I don't really believe this, but that's what he says.)

He's making this claim for two reasons: (1) to respond to the argument (not directly stated in the article, but quite commonly understood to be sound in the profession field) that it's unwise to get a PhD in philosophy because there are not enough jobs and (2) to suggest that if you do want to get a PhD in philosophy and use it professionally, you'd be wise to study with Chalmers at NYU in order to get placed into these tech-industry jobs.