Hmm . . . interesting. You have a linear polarizer that appears to be defying the laws of physics. The reason why a polarizer (doesn't matter if it's linear or circular) doesn't reduce reflections from metallic objects is because light reflected off a bright metallic surface is already polarized, so it has no effect. Now, there is an angular change from incident to reflective light, but the polarization is not changed. Perhaps this is what you're seeing.
Cf:
Polarization of light
and
https://www.physicsforums.com/threads/polarization-change-upon-reflection.175337/
Do a text search on 'metal'. Those sites explain things better than I can.
On the topic of polarizers, I actually have a comment and a question. Actually a couple of questions. First, I've never even used a circular polarizer, so I don't know if it responds differently from a linear one in this situation.
Have you ever used a polarizer to take a photo of the sky, hoping to get a nice, deep blue coloration of the sky, only to find that half of the sky was deep blue and half was not affected? Well, I found out why I was having this sort of problem with my sky photos. I wasn't pointing my camera at the right areas of the sky.
I learned from a physics class how to tell what areas of the sky are polarized. If you open your hand out flat with your thumb pointed upward, point your thumb at the sun. Now, sweep your fingers left to right (or right to left) as if your hand is pivoting on your thumb. The area of the sky being swept by your fingers is the area of the sky that will be polarized. IOW, polarization occurs at right angles to the light source. Once I found out about this I was able to position myself when shooting the sky so that the entire sky in the frame would be benefiting from the polarizer.
My second question is related to this. As I recall, circular polarizers became popular because they didn't affect a camera's metering system to the extent a linear polarizer does. Am I remembering this correctly? I'm also curious if a circular polarizer will have the same effect and follow the same "hand rule" that linear polarizers do.