Cool. I also work in that industry. I have a couple older Nitons in a drawer at work. All I am saying is chemical makeup is not the only factor in the quality of a material. Also, depending on the device and specific alloy library, there are limitations to what an XRF analyzer can tell you about the chemistry.
So PMI may tell you the material is right, but it could still be a crap bolt. That's all I'm saying.
Yeah, that's a big 10-4, but it's the first step in the process. All I'm trying to say is that if you prefer phosphate, buy from a respected company. If you want nitride or nib, buy from a respected company. If they coat a turd, it's a polished turd, literally.
And yes, collecting accurate PMI is horrid.