Sweets, I wouldn't call this CIO at all! I did it with my daughter too, ignored some of her overnight grizzles. They were half-asleep grumbles more than anything but I had been responding to every one of her wake ups. I think there is a HUGE difference from letting a child grizzle while they put themselves back to sleep to ignoring a crying / distressed baby.
Totally agree. CIO is letting you baby cry for longer and longer periods of time, regardless of the type of cry. There is a huge difference in waiting to see if your baby is just having a grizzle or if they truly need you to help. I do the same with both of mine and even did it when they co-slept. Kids can also be very noisy sleepless, both of mine often cry out while asleep or dreaming, they aren't even awake in the slightest.