Until something unexpected happens. If the DM has an emergency, and has to dive deeper to pull someone out of a bad situation, do they follow him/her? It sounds like a trusting situation where they are relying upon everything going as planned.This happens all the time, how often during a briefing do you hear the question "Does anyone not have a computer" and the hands go up.
If it's a guided dive and the divers stay with the DM and abort the dive if they get separated they'll be just fine, you know the DM isn't going to be pushing the NDL limits. You might not dive that way, I've got 3 computers on me at all times and I'm self reliant, but the vast majority of divers don't make a career of it. They get certified and dive maybe 1 week a year so they aren't up to speed and they don't want to be.
They'll be just fine
SeaRat