Counterfeit component risk and bad security for an assembled IoT device are two separate issues. Sourcing components on Amazon in the first place is ludicrous to me, to be honest, and I'd be shocked if any reputable EMS companies do it. As an aside, a couple years ago I saw some guys from NXP do a talk on component counterfeiting. People will apparently remove them from dead boards, shave a few microns of material off the top of their legitimate capacitors, change their reported value, and resell them. Pretty nuts.