No, not tearing it apart, it is about making sure that it is "tight" and doesn't come off by hand.
If take you look at my console (see attached photo in previous reply), you will find that you can't actually touch or see the fastener inside, making what you are saying not feasible. I was actually imagining it required a special tool kind of like an automotive O2 sensor socket that fit's over the hose and slips inside the console. It turns out that you have to remove the SPG from the console and fish the hose through- which is why I said "tear down". It's not destructive, or even difficult now that I know how, but it would cause physical wear to the SPG, hose, and console.
"Doesn't come off by hand" isn't the same as torqued to spec. Somewhere between 'hand tight' and 'huge amount' doesn't seem scientific enough to me for "life support equipment". I also doubt that's what the service manual says.
I have added crescent wrench and pliers to my list of dive kit essentials. If I'm ever in the position where I don't have my gear and I'm renting a console that conceals the fastener, I'll pop it out and check it just for peace of mind. Then I'll probably find out what that shop thinks of that procedure and share with them why I added that to my gear check.
One other part that some technicians forget to tighten up properly is the LP hose to the second stage.
On every second stage I've seen the fastener is visible so then your suggestion would work- you can throw a hand, or better yet a tool, on it without any disassembly. There's probably an exception to that which I'm unaware of though.
Your suggestions about "calm and non-confrontational" are spot on- that's my plan. I'm not mad at them and want to know what they suggest to make it right. Your words do seem calm, however a bit confrontational.
I appreciate you freely sharing your knowledge and experience. The details matter though.