I think their point is that a hypothetical connection-specific cert would make it difficult/impossible to compare your cert with anybody else to be able to find out that it happened. A CA could be backdoored but only “tapped” for some high-value target to diminish the chance of burning the access.

> I think their point is that a hypothetical connection-specific cert would make it difficult/impossible to compare your cert with anybody else to be able to find out that it happened.

This is already the case; CT doesn't rely on your specific served cert being comparable with others, but all certs for a domain being monitorable and auditable.

(This does, however, point to a current problem: more companies should be monitoring CT than are currently.)

Well, the cert can still be compared to what's in the CT Log for this purpose.

Yes, precisely.