For those who don't know, MacOS 15.3RC changes the behavior of Apple Intelligence and no longer provides an opt out during setup assistant. Users can either enable, or click go back, the option to setup later has been removed.
If you are an organization that does not yet allow AI, I urge you to check your beta seed documentation and submit feedback to Apple. Making changes like this in an RC release does not provide prior time to identify, evaluate and implement solutions. Thankfully we are in a good place, but others may not be.
https://developer.apple.com/documentation/macos-release-notes/macos-15_3-release-notes