As far as I'm concerned it's a design flaw.
Yes, people SHOULDN'T make this mistake, but they do. A fair number of people would still be around today, and a friend of mine wouldn't have a hole in his leg, if Mr. Glock had designed his pistol so that pulling the trigger wasn't required for disassembly.
Given that any number of people have accidentally/negligently discharged rounds due to this characteristic, then that characteristic should have been changed long ago.
Should you put the clutch in and put a manual transmission out of gear before starting the car? Of course you should, but some people don't and run over things they don't intend to. So, modern cars won't allow the starter to engage unless the clutch is in, and as a result fewer things get accidentally/negligently run over.
And for everyone who swears that THEY are too smart and careful to EVER make such a mistake—well maybe you are, but the guy a few lanes over at the range may not be as good as you, and you may absorb the round he discharges when he pulls the trigger on a loaded chamber during disassembly.
It's an outdated, flawed design characteristic that should have long since been changed.
Hokey religions and ancient weapons are no match for a good blaster at your side.