Alpha Zero is not trying to be AGI.

> The premise that an AI needs to do Y "as we do" to be good at X because humans use Y to be good at X needs closer examination.

I don't see it being used as a premise. It see it as speculation that is trying to understand why this type of AI underperforms at certain types of tasks. Y may not be necessary to do X well, but if a system is doing X poorly and the difference between that system and another system seems to be Y, it's worth exploring if adding Y would improve the performance.