I think it’s just bug.
Facebook have demonstrated capability to do accurate face recognition, and it's hardly a stretch to assume they couldn't do enough object and possibly brand recognition from a live video feed from you phones camera as you're using the app.
Perhaps people might not make assumptions or jump to conclusions like those, if the company was one that had a solid track record of respecting user privacy and getting the protection of privacy right. That company is not Facebook...
But what would I know, I'm just "a dumb fuck"...