Arless,
Exactly...A: He only does that when is "Knows" he is shooting all close targets, then switches back before the next stage. His type of competition shooting has multiple stages at multiple distances so when all or most targets are going to be close, why use a hold over when a couple of quick clicks put you dead on bull-eye? When done shooting that course, 6.2 clicks and he is back to his true zero.
I would only dial for run n gun stages where all the targets were in that 10-20 yard range. If I had a wider array of distances, then I would just use the holdovers, it would take too much time to dial up and down.
You still see Cmore's on pistols, but you won't find many on rifles. They are too hard to zero as the don't have positive click adjustments and the polymer housing is too frail for serious rifle use.