I love how some people rationalize and defend poor engineering by counting the number of successes.
I love how some people rationalize and defend poor camera prep procedures by counting the number of failures... ;-)
WSD, I'm sorry for your luck and it might very well be that there is a problem with the housing. However, as you pointed out yourself, you had done several dives, and numerous snorkel dives without incident. That being the case, the housing either isn't flawed, or something happened to it prior to the last, flooding, dive. It's unlikely that the housing suddenly developed a "flaw", so the logical conclusion is that something (and by that I mean an o-ring) either was pinched, or had something on it... a hair, fleck of sand, even a grain of dried salt.
I've been taking cameras into the water pretty much weekly for, I think, 36 years, starting with a Nikonos III and most recently a DSLR in an Aquatica housing. I have never flooded one (I'm knocking on my wooden head currently) and I credit that to a bit of luck and a lot of meticulous care in the preparation of my cameras.
It sucks to flood a camera, but with the gazillion or so GoPros in the water on a daily basis, to make a blanket statement like you have is a bit much. Send the stuff into GoPro and plead stupid and maybe they'll fix you up. If not, chalk it up to experience, buy a new one, and be more careful in the future. And be glad you didn't flood a $5000 Nikon.