No pope has spoken ex cathedra on a matter of faith and morals to the Universal (Catholic) Church since prior to the Second Vatican Council. In other words, no pope has spoken infallibly in that time frame. So drop your strawman; it’s tiresome.
Dude, they’re never drop their strawmen. Their house of cards is built of strawmen. If they dropped their strawmen, their silly heresy would have to be thrown under the bus!
So the pope, seeing Vatican II, has decided not to object to it.
Is his silence also infallable?
I would say no pope has ever spoken infallibly at any time.
Since a Pope decided he was infallible, and was in error to do so, no Pope is ever infallible.