So here are some example shots, first from the pixel, then from the 6p. Mind you I'm not a professional photographer, I just picked up the phone pointed and took the photo. Obviously with a little bit of actually trying to make a lens flare happen.

This is what we are seeing, both in that video and in the OP's initial post. Then below we see what the 6p does in the same situation:

This lens flare occurs on the 6p as well. In the second photo you can see the lens flare underneath my dog's water bowl. The flare on the 6p is nowhere near as noticeable as on the pixel, but it is definitely there.
Bottom line, this is something that all cameras are susceptible to, sure. But it seems the pixel is more susceptible to being photo-killing than normal.
Also of note, I tried to recreate the same purple Arc that the pixel sees on the second photo on the 6p and could not do so.