Ok, I normally avoid these debates because minds don't usually change but it has been polite so I will indulge.
I would not say that the i3 is perfect. Nothing is. It can inflate on a crowded boat...but I never found this to be a problem. Loss of a couple breaths at best. Would I wear it if I were crawling in muck trying to find a lost ring or penetrating a wreck, No. But most divers don't EVER do those things. Can it stick yes, it can but in my short diving career, I have seen the standard inflator buttons stick more often than the i3, so do I think it is more likly to fail..No not if it is maintained.
On to the scenario. SS in your scenario, my equipement has failed, I am incapacitated, my dive buddy has abandoned me and you are level headed enough to rescue me but only if you are not too confused by my lever. Ok if all of those things happen I am in trouble. BUT one can cover all kinds of scenarios like this that don't validate the argument.
What if I am a diver with 500 dives and you are at 60 feet with a tank on your back and a sidemount and you are wearing a drysuit. I have never dove a drysuit and don't know how they work. I swim up and see you clutching your chest. I might try to get you to the surface immediately so I inflate your BCD and bring you up about 20' at which point you go inverted and rocket to the surface. Clearly driving with a dry suit is overly dangerous because a wetsuit can't fail but a drysuit can.
My intent here is not to make light or belittle your legitimate points but there are all kinds of imaginable situations. I can easily imagine that you caught your valve on a rope in a wreck while exiting up and are inverted and hung up but need to go downward to untangle the valve. You pull on your dump valve but it doesn't work because you are up side down. If you had the i3 the lower port on you vest would dump and you would be able to descend
On one of my most recent dives, a DM with over 3000 dives could not lead the group because the 2 year old plug on his high pressure port blew as he was gearing up. Another diver had air bleeding out of 4 inches of his low pressure hose. Neither situation causes a chorus of 'don't do it, it is just a gimmick to sell gear' like the i3 does.
Just as some shops may try to sell it, other shops that don't sell it may try to belittle it because they don't sell it.
I love diving with it because it makes the minute by minute dive easier and more comfortable.
Each diver should decide for themselves what is best for them.