It should matter to a degree, since the U and C books are viewed as different colors technically to the software, they separate as two plates, not one, unless pre-press looks for not just identical duplicate colors, but also near-name duplicates and replaces one of the colors, such as the U, and makes all of the them the same, like C. Its a headache for pre-press, and takes time, which takes money, your money.
My goal in all the jobs I send to print is that the pre-press people would have a very straight-forward experience with my files. Best complement I ever got from a printer was that the files I gave them were the simplest and cleanest they ever saw. The goal is always to make as little confusion for the pre-press and printer as possible. Makes your life easier, your time-billing from them cheaper, and your relationships with your venders stays strong, which often translates into preferential pricing over time.
Perhaps I wasn't clear. I know U and C are viewed as different colors, and yes I know that it matters how a color is named (that is, PMS 185 C vs. 185 U for example), and that there must be consistent naming of a spot color for correct seps in a spot color job. I have worked as a Prepress tech and graphic designer for many, many, many years and have corrected several such instances of the issues you're referring to.
What I'm saying is that if one of the colors used in a given spot color job is, for example, PMS 185, then it really doesn't matter whether the color is named "Pantone 185 C" or "Pantone 185 U" or "Hey this is a red spot color" or any one of countless other names, so long as the pressman knows that the actual Pantone color to print for that sep is Pantone 185. And in my case I choose to use "Pantone 185 C" as a name because I prefer that over "Pantone 185 U" as a name. That any spot color must be consistently named and applied through a given job for correct color seps was assumed in my previous post.
Now, don't take that to mean that I think it's okay to use generically named spot colors, because I don't. I merely stated it that way to make my point clear. I think it's sloppy to name spot colors that way. I don't use them that way and I don't like seeing them setup that way in supplied files for spot color jobs, especially when they don't actually reveal what Pantone color is to be used. The exception to that is when generically named spot colors are used in 4-color jobs. It doesn't matter in those cases because all spot colors will be converted to process anyway.