I suppose if you are used to dealing with lights that use the frame ground, perhaps it's okay. Personally, I get asked to help fix people's lights now and then, and get annoyed trying to figure out how things can go wrong. I've seen cases where the taillight and headlight have a grounded terminal, and the ungrounded taillight wire gets plugged into the headlight connection that is grounded. Seems like the manufacturer could at least have some form of polarized connectors when this is possible.

On the plus side, it is sometimes possible to open up the light and cut/break the connection to the grounded mounting point.

Steve in Peoria