I think it depends on the quick-release. You are correct in that there was a model of the Mocke leash years ago that had a kind of squeeze release that could be twisted into undoing itself.
I added a quick-release to my belt-leash; I've used it for more than ten years without any kind of issue. It's the kind used by kite-boarders - there's absolutely no way it can release itself. (Well, never say never, I guess - but given that it's used by millions of sailors and kiters, etc, it must be reasonably reliable!)
So I'd yes, absolutely, the so-called quick releases that come on some leashes should be avoided, but a properly designed quick release is great - I quick-release my leash every time I come in at the end of a downwind...
Rob
Currently Epic V10 Elite, Epic V10 Double.
Previously: Swordfish S, Evo II, Carbonology Zest, Fenn Swordfish, Epic V10, Fenn Elite, Red7 Surf70 Pro, Epic V10 Sport, Genius Blu, Kayak Centre Zeplin, Fenn Mako6, Custom Kayaks ICON, Brian's Kayaks Molokai, Brian's Kayaks Wedge and several others...