As an electrical engineer (BSEE), people like me are sometimes asked to be expert witnesses in court cases about electrical safety liability. In the USA, electrical safety is tested, and accepted most readily in industry, by Underwriter’s Laboratory (UL). Unfortunately this testing is expensive, and if a Chinese LED light maker pays for the UL certification, the cost of their lights will be much higher (and the certified product will have a “eXXXXXX” number on it). But UL certification shows that a third party has inspected the power supply to be safe, instead of just the maker of the product
saying it’s safe. Also unfortunately, none of the Chinese LED lights described above are UL certified, as far as I know. This problem becomes bigger because the
metal case of the light (metal is needed to remove heat) is what “protects” the wires and electronics inside. However this metal case in not hermetically sealed (not truly “waterproof”), and indeed because of the $5 cost it is often rushed through assembly where even the rubber seals are incorrectly inserted, or forgotten altogether. Here is an example "waterproof" light from ebay, fresh out of the box; you can see the "waterproof" seal on the 240/120 volt wire is completely not sealed. See photos.
There have been cases on aquarium forums, and on youtube, where the metal compartment screws have not been tight, or were missing. Ground wires were loose, or just cut off. Internal drivers loose and rattling around. Heat sink compound too thin or missing, causing overheating and melting of wire insulation, and even causing steam from water that was splashed on it. Because of this, it’s my personal opinion that using these metal bolt-on LED lights is potentially unsafe in the saltwater environment of scrubbers which are setting on sumps. Googling “chinese led light danger” finds too many results to read, but here are typical ones: