I look at things like that from a revenue/strategic perspective.
If Apple says it, do they have any disincentives to deliver? Not really. Their ad business is still relatively small, and already architected around privacy.
If someone who derives most of their revenue from targeted ads says it? Yes. Implementing it directly negatively impacts their primary revenue stream.
IMHO, the strategic genius of Apple's "privacy" positioning has been that it doesn't matter to them. It might make things more inconvenient technically, but it doesn't impact their revenue model, in stark contrast to their competitors.
It's certainly possible through remote attestation of software. This is basically DRM on servers (i.e., the data is not decrypted on the server unless the server stack is cryptographically attested to match some trusted configuration).
That requires trusting that the attestation hardware does what it says it does, and that the larger hardware system around it isn't subject to invasion. Those requirements mean that your assurance is no longer entirely cryptographic. And, by the way, Apple apparently plans to be building the hardware.
It could be a very large practical increase in assurance, but it's not what they're saying it is.
I haven't read all the marketing verbage yet, but even 'Our cloud AI servers are hardware-locked and runtime-checked to only run openly auditable software' is a huge step forward, IMHO.
It's a decent minimum bar that other companies should also be aiming for.
If Apple says it, do they have any disincentives to deliver? Not really. Their ad business is still relatively small, and already architected around privacy.
If someone who derives most of their revenue from targeted ads says it? Yes. Implementing it directly negatively impacts their primary revenue stream.
IMHO, the strategic genius of Apple's "privacy" positioning has been that it doesn't matter to them. It might make things more inconvenient technically, but it doesn't impact their revenue model, in stark contrast to their competitors.