Voltage readings perfect throughout the range of idle, mid, and WOT.
Cause of concern: selling the truck.
Found resistor in LED light board burnt out - causing light to stay on - replaced and is now good as new - dealer stocks these items as they sell often.
P/N: 30595 for those who may need it in the future

describe further "normal" as far as voltages, at rest, starting (with load) running at idle right after start, and then wide open throttle. then confirm no voltage drop by reading voltage though the meter with the cable disconnected from the battery/ key and lights off, reading between the disconnected cable end and disconnected battery post.
OR ignore it, if everything runs good, it may be that someone before changed it to a 1 wire alt. what made you decide to be concerned? what made you put a new battery in?

Possibly is a broken wire from the alternator connector up to the light,or the light it's self.....I don't have a schematic for it just going by how other trucks are wired that I've looked at