It is at least possible (if not likely) that Apple has a special deal with ARM that lets them get away with all this.
Which may mean that ARM wants them to be quiet about. Not because Apple is breaking the rules, but because ARM doesn't want to rub into its other customers the fact that Apple has a special deal that other customers aren't being offered.
This sounds the most likely, tbh. Apple has been breaking the spec for years, but they’ve been very testy about ever mentioning their custom extensions and ARM has probably agreed to look the other way as long as they don’t draw attention to the fact.
> ARM has probably agreed to look the other way as long as they don’t draw attention to the fact
That makes it sound like it is some kind of "tacit understanding", "I won't say anything if you don't say anything". I'm suggesting that maybe Apple's license agreement explicitly states that they are allowed to do all this, but also maybe its confidentiality clauses prohibit either party from publicly acknowledging that fact without the other party's explicit permission.
A company like Apple – who has a well-funded legal department, and I've never heard any suggestion that they are anything other than competent – wouldn't set up a multi-billion dollar business on the foundation of "agreed to look the other way". They'd have it all set out in writing, crystal clear and totally secret.
Plus their funky intel-emulation related CPU features which introduce architectural EL0 state (SSE-specific FP flags, AP flags). Plus their hardcoded VHE=1 spec breakage now becomes relevant at EL2. And almost certainly more things we haven't figured out yet.
Which may mean that ARM wants them to be quiet about. Not because Apple is breaking the rules, but because ARM doesn't want to rub into its other customers the fact that Apple has a special deal that other customers aren't being offered.