I see what your asking and yes some people choose the monkey around CMYK values their input files which in my option is a recipe for disaster.
I monkey around. i just wasn't sure what he was saying.
However, I don't edit the original library, I'll copy-paste to a new library that's specific to a client. We've had clients edit the printed colors eventho we all agreed that it matched the book.
One funny issue... if you edit a color in a sub-library and that library is higher on the list than another client's sub-library or the main pantone library, then the spot color will re-map to the top library. ... I'm sure y'all know this, so not new info.
However, someone monkeyed with a client's color, messed it up bad, and then i guess had to leave for some reason? They nuked all the colors, so the spot was printing white/paper.
I had a different team member print a different a different client's project that used the same PMS designation. Except the client's logo was printing white. My team member printed 1500 sheets not realizing and delivered to the client.
No one in the shop could figure it out and they eventually asked me. I tore the file apart on the front end, looked in the settings, pulled out hair... only to eventually dig into the spot libraries. I couldn't even process that would be the cause since no one would mess up the spot build, so it was the last place I looked.
So, yes, to your point, monkeying with spot values can be a disaster!
I asked the team if they could move client specific libraries under the pantone libraries when jobs were done... but they wouldn't. We (I) made it part of the (my) calibration protocol to make sure the actual pantone libraries were at the top of the list on a regular basis.
It's like cleaning the kitchen because team members can't be bothered to wipe up their coffee spill! Your mom doesn't work here. Clean up your own damn libraries. nope.
Okay, rambling over