Whether or not one can tell it's AI generated, one can certainly tell it's not Knuth. For one thing, the writing style is very different. Not that there haven't been other great computer scientists who may have written in this style, but it definitely doesn't sound like Knuth (there is no "being a bit cheeky" for sure). But also, the ideas it has produced are simply more of the same; kind of a natural progression / what a typical grad student may write. Knuth always has something new and surprising to say in every paragraph, he wouldn't harp on a theme like this. Also he mixes “levels” between very high and very low, while the paragraphs you quoted stay at a uniform level.

But of course, writing as good as a grad student's (just not the particular delightful idiosyncratic style of a specific person) is still very impressive and amazing, so your concerns are still valid.