The problem is that having that rule results in those 1%s always being excluded. It's probably worth just going back and looking at the arguments for laws around accessibility.
I'm somewhat tempted to think that whoever sued berkeley and had the whole thing taken down in this specific case was just being a knob, but OTOH there's issues even with that POV in terms of letting precedents be set that will de facto still become "screw over deaf people entirely" even when everybody involved is doing their best to act in good faith.
Hopefully speech-to-text and text-to-speech will make the question moot in the medium term.
I really think this and other tech advances are going to be our saviors. It's still early days and it sometimes gets things wrong, but it's going to get good and it will basically allow us to have our cake and eat it too (as long as we can prevent having automated solutions banned).