Generous? If OP has as many people as our world, there would be 1000 people with CoC, and the OP world likely has more. Chinjao himself said that having CoC isn't enough, Luffy will encounter tons of people with it. The difference between the New World and the Grand Line is just having CoC is impressive in the latter; in the former, you need to have exceptional CoC to be impressive. None of you should be surprised.
That's not the point at all.
Besides that fact that the majority of people in the world are just civilians and aren't top tier fighters among pirates or marines. You already lose like 95% of all people with CoC who have a dormant ability but work as a shopkeeper or whatever.
Another thing is that 1 in a million is just a figure of speech of how rare it is. But at this point in the story it doesn't seem rare at all.
The original point is, if everyone has it, there is no point in having it in the first place because it levels the playing field. Why can't Luffy have an edge on enemies with this thing ? Probably every foe he will face from now on will have it. I can't imagine a yonkou or an admiral without it. Apparently a yonkou first mate also has it. So Oda has been handing it out like freebies.
Why the shock at marineford that he used CoC, there were probably 10 people there with that ability in hindsight. Did it really make Luffy that much dangerous ?
What did it add to the story that Dogtooth showed CoC today ? Would it be too much if Luffy on his own knocked out Flambe and her goons ? That would also give him an slight extra advantage over the already impressive Dogtooth. But by giving him the same Luffy also needs to overcome that again.