Are you saying that the cyan filter (and presumably the magenta and yellow filters) in color enlargers have substantial neutral density components in addition to their "advertised" colors? If so, this seems a bit surprising to me, but as my own enlarger (a Philips PCS130/PCS150) uses an additive color system, I can't do any tests to check this. Certainly with mine, adjusting "cyan filtration" (really red light intensity) has no discernible effect on B&W VC papers.
If you look in the Kodak filter books you will see that no filter is perfect. A perfect filter is a rectangle in absorbance or transmittance. So, yes, what I said is true.
In particular, a cyan filter has a lot of green and blue absorption, etc.