Did you miss that he started the dive with a DSMB?
It's not my example. Someone else brought up a real situation to explain why a new diver should carry a DSMB in case he gets separated from your group and in that example, the diver actually had a DSMB at the start of the dive but managed to lose it so it didn't do him any good.
For the third or fourth time, this isn't a general question as to whether DSMBs are valuable, it's about whether it's valuable for someone with only a handful of dives and no training on deploying a DSMB diving with this dive op in Coz.
IMO, the risks of a person in this particular situation of trying to deploy a DSMB at depth are unacceptable. Especially if stressed by being separated from the group and whatever conditions caused the separation.
Can we agree on this advice to this diver on this vacation? Go ahead and take a DSMB, but leave it in your pocket while under water until you have a chance to train on deploying it. You can take it out and blow it up on the surface if you need to use it as a signalling device.