Earlier quoted context omitted.
Likely not, some pickup trucks can "force" the backup lights on as "bed lights" it seems. When parked, the car doesn't have tons of requirements vis-a-vis the lighting (the laws are usually worded like "when in reverse gear, two rear-facing white-burning lights must be visible with a power of X lumens" or something).
Um, what truck bed can be lit by using the reverse lights? The only way I can see this working is if there's another truck behind you so that your reverse lights are pointed at the other truck. Truck bed lights have always been behind the cab. I've never seen reverse lights considered as bed lights.
And with that it makes sense as a safety feature - if the only way to turn those on is go into reverse, people would be tempted to throw the truck in reverse and leave the parking brake on while they jump in the back to look for something. Unfortunately it seems not all of them are locked out as I've seen trucks driving on the freeway with the reverse lights on.