Growing up we had plenty of quail around. These days my old stomping grounds are barren. Lost to urban sprawl and a lack of habitat. Golf courses don't grow quail. Even with many birds we only shot the covey rise, never hunted the singles. We always quit fairly early in the afternoon so the the scattered birds could whistle up before dark to roost. It was all about the dogs and experience as you stated. My experience puts me firmly in the conservation camp. I still thinks it's a little over the top to bar 12 bores with loads that are the equivalent of small bores. Kind of the wrong execution of the right idea so to speak, but I understand where they are coming from. It limits the use of some fine old quail guns. Using the old guns is part of the charm for me.
Yes, the concept of limiting a hunt to a SxS or O/U in small bores on quail preserves, upon closer examination, makes little sense, as in actuality, the birds are released, there is no limit, there is no deterrence or hesitancy to overkill for the benefit of spring nesting, and the birds put out will all pretty much be dead within a few days from either other hunters or predation. Some places will put out loads of birds and simply charge for the excess, on which there's some degree of profit margin. Others have self-declared daily limits, which I'm sure is a function of bird availability.
When it comes to using the 'proper" guns, as they say,
"Image is everything." 
