tl;dr the action would allow carriers to default to blocking calls on the part of their customers. Once SHAKEN/STIR (caller ID authentication) is available, this means carriers can block calls that don't include authenticated caller ID. Presumably they already could do this if the customer opted in.
This all seems like a good idea, but I think Pai is overselling it a bit by calling it "bold."
Is this really true? How absolutely dysfunctional things must be.
You either need to update regulations on a fast time scale, or a way to encourage actual competition (so the heavy anti-trust-like regulations aren't required). Otherwise, you've just given up on there ever being meaningful progress/innovation in the industry.
That said, this is exactly what a competent FCC should do - in the absence of a larger ruling to require consumer-protecting behavior to be implemented by carriers, it should seek to clarify existing rulings - which is exactly what is happening here. Carriers interpreted an older FCC statement to prohibit them from blocking robocalls by default, and it's likely this was never the intent.
I don't think that's all of it by any means, but there are a number of ways that the carriers can tell that some percentage of the calls are bogus without having to ask the receiver if they want to receive it.