Pantone designators and/or cmyk

Often I find that companies request a particular pantone color they would like to use for their logo along with the cmyk equivalent.

Is it not imperative to give the pantone designator that comes after the number? i.e. 286 "C" or "CP"

I'm usually only given the number portion. Let's use these as an example

Pantone 286 or C100 M66 Y0 K2

Go ahead make those two separate shapes using Pantone 286C and the CMYK values. The colors are nowhere near each other. 286 CP, however, is much closer to the CMYK value.