"No original vocal...100% flange" could be taken more than one way.
At one extreme, simple time domain alterations, stretching and shortening the original signal, discarding all original so there's no audible phase interaction, just the time domain element.
Other extreme, 100% wet output, with comb filtering, cancellation and summation.
Either way, if any two samples purely sum...the potential over could be as short as the sample rate.
There's a limit to what popular spec A's can show, but it is theoretically possible you have the waveform that will tell us all what the effective attack in CL is, or at least one endpoint on the spectrum of possibility.
Before you dig into any of that...this also may have absolutely nothing to do with your overs or CLs attack. It's also possible the release rate is the culprit but flanging and modelling being what they are, my guess is "attack" or "other".
(Typo)