We all know it's not about age, it's about user identity. As above, it's clearly a wedge so it's not rhetorical to observe more invasive and controlling features are coming.

Simple attestation is very useful for the case where a parent gives a child access to a computer and wants that computer to block porn. That's the use case everyone is clamoring for, and asking the root user "how old is this user?" solves it in a simple, open, privacy-preserving way. Everybody wins, except the teenager who wants to watch porn. If this were not legally mandated, everyone would support it as a useful feature, but since it is legally mandated, we have to get angry about it.

Literally the entire purpose of the law California passed, which Linux is responding to, is to preempt such laws: If someone says "we need identity verification because think of the kids looking at porn", it's now trivial to say "we already solved that problem, without deanonymizing everyone on the internet".