Turning a whole person into a moving light source would be an absolute nightmare. You'd have to either use practical effects (e.g. a dude running around with a light ball then masking them out) or fully model and composite the new lighting into every scene and also composite the lighting onto the character.

They probably attempted it, but the look was off because they didn't shoot the scenes on set in a way that made it easy in post, so they scuttled the idea. What this person is saying is just them saying "yeah, that shit looked weird and reshooting the scenes to make it look right would take months that we don't have".