One parameter would be: Amount of money this customer has spend on our products.
Another would be: Active time since signup.
I'm pretty sure if "money spend > 0" is actually a legitimate threshold to remove a lot of spam, although not all. "money spend > 200" might to the trick though.
Unfortunately the best way to do KYC is (still) human intervention (and use of data).
Of course this still isn't a perfect metric. But it seems that banning people with accounts that have spend thousands of dollars and been active for many years should probably be avoided and this will significantly help that.
I mean if the account has spent >$50 you can probably afford a human review at the very least.
As a general rule of thumb, if Google is struggling with a problem, it's not a tech problem.