I've run this experiment on myself a great number of times.

Your story is correct, sometimes. It's not correct all of the time. Sometimes AI is slower and the output is better (think: pair programming). Sometimes AI gets me the first draft and the cognitive understanding takes time (overall, for me, usually faster, but sometimes slower I will readily admit). I'm really good at reading code, I guess? And still other times it will one shot near perfection (in true slot machine fashion). It'll also produce absolute shit, as well, frequently.

My firm point to you is it's not a blanket truth.