.....Which is an effect of the first satisfying first order approximations while failing higher order rules, while the latter is merely an unusual sentence and so requires more effort to parse because it falls off the "fast path". (It also arguably fails to encode embedded cultural messages present in word choice -- a second consideration for why it feels "awkward": it's valid English, but not my tribe's English.)

You haven't pointed out how semantics is anything but higher order syntax -- merely outlined the way in which higher order syntax interacts with our perception.

I agree that there's a difference between the two sentences -- I disagree that it's because they're different fields of study instead of different edge cases of the same underlying notion of parsing syntax. (I especially disagree that the way forward on teaching machines language involves that distinction.)

I would appreciate you referring me to references on the semantic/syntax divide being "natural", though.