> That is technically actual fraud.
That would depend on whose laws you were applying. In a lot of places, fraud requires a misrepresentation that's actually material to the transaction, and a court could come down on either side of the question of whether the user's age was material in the necessary way.
> Google opens themselves up to huge liability if they inadvertently do business with a minor, which is why they're so paranoid about the lock-out.
No, they really don't. They might open themselves up to limited liability if they let a minor do something that lost said minor money. They also might not be able to enforce some of the "take it or leave it" provisions of their terms against minors (of course, in a sane legal system they wouldn't be able to enforce those terms against anybody, but you don't see many if any sane legal systems).
But they do not open themselves up to "huge liability".
Nonetheless, they don't choose to take even those small risks. Mostly, I suspect, because the response wouldn't be automatable. Google hates anything that's not automatable, and vehemently resists manually fixing anything. That applies to interacting with adults, too, and to cases where you haven't even actually violated their policies, but the automation happens to be wrong, which happens all the time.
Which is why nobody of any age should be depending on Google.