Mark,
I disagree with you. Or should I say, photographs disagree with you. I have early photographs of all the courses I listed and the sand is flashed to the top in many cases and flashed high up the faces on many more. Flynn flashed sand up the faces on most of his bunkers, though he would vary the amount of grass showing. I do not use the definition of flashed sand as you do, with sand all the way to the toplines of bunkers. Regardless, a majority of Flynn bunkers had sand flashed well up the faces, with quite a few all the way to the top. It is a fact. Pictures do not lie.
As for Flynn's design principals not allowing a different design style for resort play, I think you are wrong there as well. First of all, I wouldn't call it "dumbed down." Secondly, like any architect, there was some direction from the resort and owners. Flynn designed other public golf courses that were rather benign in comparison to other designs and he designed 2 courses at Boca Raton that were among the best in America at the time. They had wide fairways but severe shot demands if you strayed off the ideal line of attack or into the hazards. I'd say he would design for the course requested. If given the freedom, he would lean towards championship designs. The primary reason for the bunker depths at Cascades is likely the rocky soil. But I wouldn't discount some component being what the client wanted and was willing to pay for. That was an expensive and vast construction project. It was not nearly as laid on the ground as you originally believed.