It sounds to me like a lot of these minor indicator movements (slight dip/sideways) would have been line bumps and not bites (unless you are dealing with tiny fish, which I don't think you were). I've watched the trout swarm around flies under the ice and on camera. They hit the line quite often when using more than one fly.
It's an interesting thought about indicator size. I can't say that I've noticed a difference in hook up rate between sizes. Sometimes all I see with the big indicator is the rotation of the toothpick or a slight vibration. They have it. It has been our experience that the bigger the fish, the slower the take. I think big fish are often slowly grazing around sucking in their prey and not in a hurry. Things can change during a mass bug emergence or minnow hunt, but generally big fish are quite lazy.