Why exactly?
Diver's pay good money to make a dive. Besides the cost of the dive there is often transportation and hotel expenses involved also. Sometimes the weather or the seas do not cooperate and a dive must be cancelled or a new location found. That is beyond the control of the dive operator. However, to need to cancel or change a dive because of an equipment malfunction of the Divemaster's gear is unacceptable. The Divemaster should have had an extra set of gear to use, either personal or from the rental inventory. So in my opinion he is a fool. The fact that he is so experienced and an ex-commercial diver makes him an even bigger fool because he should understand redundancy.
I am also a bit skeptical of Tater's story of the Divemaster's plug blowing out. First, in over 20 years of diving I have never heard of such a thing. Second, as a hobby I do like to fix and restore old dive gear some of which is well over 20 years old and never seen an internally damaged port plug. Third if the plug actually "blew out" as was described think of the velocity it had. It would have shot far from the first stage and would have been virtually impossible to find.
However the above is speculation, let us take Tater on his word. The plug blew out as described because of a manufacturing defect. So should we use more port plugs (more complex) or less of them (less complex)? Tater's point of view appears to be complexity does not matter because even a simple piece of machined metal can fail. That view is not logical, a rational diver should arrange his gear to minimize failure. A rational diver should also test and inspect his gear before a dive to spot potential trouble like leaky hoses. I suggest you do a bit of research about "failure points".
In the real world it is not unusual for inflators to fail. (Both Halcyon and Apeks had inflator recalls) I had it happen. However, a failed inflator can be replaced with a spare inflator in less than 5 minutes assuming the diver has a spare (with zip tie) and pliers. At a dive destination any dive shop should have a spare inflator. If an I3 fails then it will require a trip to the dive shop and not all dive shops are qualified to repair it. So if it fails at a dive destination, the diver would need to rent a BC which would in all likelihood have a conventional inflator that he is not use to handling. Tater is also of the opinion that as long as the mechanism is maintained and serviced at a dive shop it should be reliable. However, most experienced divers will tell you that the probability of problems are higher after a service than before.
