I'm ok with that. I'm still on an old data plan that throttles me after I got the limit for high speed data. But they don't hide that limit or my usage, and it's really cheap.
I don't want to pay for unlimited data, and I don't want to lose data after hitting a cap.
Everyone is ok with being sold something that they understand, most people are not ok with being sold something that screams "UNLIMITED" and then uses fine print to limit your seemingly unlimited plan.
Maybe the plans you're describing could spin the feature as "throttled for your pleasure" or some such. I'm sure there are marketing people that can come up with a positive way to spin it that isn't a borderline falsehood.
Only if you're maxing out all the time. I had a plan with a similar sort of thing, even after using up all my "fast" data I had enough bandwidth for regular browsing and streaming music.
I don't want to pay for unlimited data, and I don't want to lose data after hitting a cap.