I think the concern was more that if I can XSS example.com, Google is now serving that for some period of time after example.com's administrators notice + fix t

I think the concern was more that if I can XSS example.com, Google is now serving that for some period of time after example.com's administrators notice + fix this. (In the absence of a mechanism to force AMP to immediately decache the affected page(s), that is.)