It is certainly possible that I'm misinterpreting it. But it's hard to see how that could be the case with respect to the visible requirement, since the language for visibility isn't ambiguous.

From what I can tell, what you're referring to is inline validation, which is outside the scope of the new Error Prevention guideline as currently written (it is within scope for the old WCAG 2 series Error Prevention and Error Identification criteria).

I think it's likely that the new practice will be that the help text displays above the text box to accommodate this guideline. They'll probably have a carve-out for the scenario where the control is near the bottom of the page (where autocomplete obscures the label and help text).

I share your hope that the language will be clarified in the future.

Thanks for reading and commenting!