I was taught to use my suit for buoyancy control, and I had a lot of trouble managing it. Then, in Fundies, I was taught to put the minimum in the suit to remain more or less comfortable, and use the wing for the rest. This basically ended my uncontrolled ascents, at least when unmolested. A couple of years later, I took a class from the guy who started the whole "20 foot squeeze" concept, and he wanted us all to put MORE gas in our dry suits. I found I was more comfortable and warmer, and I had gained enough facility with venting a suit that it wasn't a problem to do this. My takeaway message was to put the air in whatever WORKS for the application you have. In very cold water, with a single tank, I can put all the air I need for buoyancy in the suit and manage it, and I'm warmer. With a technical setup, my suit won't HOLD enough gas to get me neutral with full tanks (unless I close the valve, which I won't do) so I split the air between the suit and wing. In caves, I don't want any more air in the suit than I absolutely HAVE to have, because I may end up going head down to follow a passage, and be unable to find anywhere later to get the air out of my feet (and diving with floaty, expanded feet is an absolute nuisance).
But I think at least one of the reasons for the difference in teaching between recreational and technical classes is simply that, if you are starting a dive 15 pounds negative, you just plain CAN'T manage your buoyancy with your suit.