Yes, I meant that not everyone actually turn their phones off, most just switch it to dot not disturb mode, which is overridden by those emergencies alerts.

And as for enforcement, yeah there isn't an effort in trying to avoid anyone sneaking in an extra phone, it's basically grounded on good faith and the fact that if they catch your phone with you (or even if it rings in the bag), you're eliminated from the exam. That's where I think the chaos would arise. If everyone's phones alerted at the same time, the examiner wouldn't know what to do.