When you get $thing from China and it comes with a "5V 2A" PSU that weighs 40 grams, has a single diode rectifier at the input, logic consisting of two transistors, no Y cap, no feedback, and a transformer with a single layer of tape and enamel separating you and AC mains.
It's actually designed for that option. See the 3 AC input terminals? Two go to the rectifier, one goes straight to the output so they can use it when only one diode is mounted, without needing a bridge.
