I would describe it as entirely normal. My experience working in a research organization where the majority of my colleagues hold Phds is that education level has a strong inverse correlation with ability/willingness to care about such mundane chores as spelling, grammar and arithmetic.

I'd call him a little bit sloppy, in need of proofreading. Certainly not an overuser of AI. He writes at least one of these monster posts a week on top of (IIRC) teaching in college, so it's understandable if he's in a rush.

And yeah, it's not the best, but it's really not worth discounting his writing more than he himself already does at the end. Lots of smart people have imperfect language skills.

A blogger.