This is just an ad hominem attack. Doesn't seem like the author is "in over their head"; they seem to have a pretty solid grasp of actual identifiable gaps between implementations and various specs, and the article was written with the same kind of "chastising" tone as you would see from any grey-bearded hacker who's unsatisfied with the way things are.

This is the same author who found and reported ABI incompatibilities between clang and gcc: https://faultlore.com/abi-cafe/book/trophies.html — Given these incompatibilities have since been addressed, I think it's fair to say there were indeed issues with C.

Regardless of your opinions about the author, that’s a pretty shallow and condescending take.

It is exactly as you describe.