Yeah, saw that, thought I'd check a few. Didn't find any capacitance vs. voltage info in datasheets from several manufacturers. Sounds like information that is only divulged on request. I'd say this is a dirty little secret of the MLCC manufacturers.
That because it's not something they probably want to brag about. 
I always felt in my gut you whimper snappers using all ya fancy schmancy SMD sized stuff were headed down a path towards evil. Excuse me, my lawn is calling.
Lefty