I have never caught and released a CC but I continually can see them come to a bait, look at it or smell it and turn and leave it. I can once in a while catch one after the feeder goes and they be distracted due to the pellets. I now catch most on live minnows probably due to the movement of the minnow and not noticing the line or hook.
I have seen the very same thing now with the HSB. I can only catch them on live minnows. I have also never caught and released a HSB but have seen them come to a minnow on a hook and quickly turn and leave. I have thrown live minnows in the water and they attack them quickly but as soon as I put one on the hook they swim up to it and leave. We still will catch one of each once in a while but nothing like a couple years ago. Our water it quite clear and I am sure that has an effect but I think the hook shyness is for sure learned. Needless to say our CC and HSB are getting quite large.