Seems if you scroll around shopping websites and look at the negative reviews you always see people saying things like “never worked at all” or “stopped working soon after”.
It can’t really be that involved to line a small enclosure with some metal fibers, can it?
The most reliable way to know if a Faraday bag works is to test it yourself - put your phone inside, call it, and if it doesn’t ring or go straight to voicemail, it’s blocking signals effectivley.