what's all this about...

The short answer is NO.  Chokes display resonance and this means they have a non-flat response.  Whether we are looking at CMRR, Choking Impedance, or Loss the response is always a function of frequency.  CMRR and Choking Impedance will always displays "peaking", as seen below.

If someone tells you they have a choke with a flat, or nearly flat response, you know that they do not know what they are doing or they are trying to fool you.

Any Common Mode Choke will display curves similar to those shown below.  The details will vary, but the overall shape will always be similar to these.