I bet you if you did a bit of a search there are multiple threads on "is my metal detector / x-ray a CCP or not?"
You can argue it both ways. BUT just because your x-ray isn't effective or validated against all foreign material, does that make it not a CCP? I think that's what your question is asking.
Ok, my response is "no". You define what your significant hazards are and presumably you've defined one as metal. And for me, question 3 in the codex decision tree always makes me say "yes" to CCP on these kind of devices, i.e. "Is this process step specifically designed to eliminate or reduce the hazard to an acceptable level?"
(That assumes of course that you've not already decided the hazard is controlled by prerequisites.)
It doesn't mean glass isn't a significant hazard. It might mean you control different foreign matter hazards in different ways, and that's ok.
Metal detectors and x-rays are odd ones in that they are a tool to control a hazard which is not 100% effective and in the absence of it working you would not say food is automatically unsafe (which in a way is pretty much what a CCP should be). There are plenty of restaurant kitchens using a lot of industrial machinery but not having metal detection. Is that unsafe? But because of the sheer quantity of kit and difficulty in maintaining it to 100% in real high speed manufacturing, I'd be loathe to remove it.
Anyway, I'm being verbose. The main point is, can you defend it? The secondary point is, does it matter if it's a CP or a CCP on your controls? If the answers are anything other than Yes and Yes, then make it a CCP.
The older I get the more I get tired of fighting and more inclined to go with the majority view if it makes zero impact on what I'm doing. If you'd control the hazard in the same way then is this the detail you should be spending your time on? Or is it the fact that half of your staff probably aren't doing what at least one of your procedures tell them to do most of the time... (I'm guessing but I'm also pretty sure I'm right.)
Basically, is this worth your energy?