Got it. There was a red tab (like many wiring connectors) hidden above that wiring contraption... seriously would be impossible for anyone to see with their own eyes... only saw it from a picture I took from above the connector. Pulled that red tab up toward the sky, pressed the black tab (below the gray hinge thing) inward... and the gray hinge thing folded down easily and the whole plug came out without issue.
Removing that tailgate was a major PITA... it doesn't have quick-disconnect support cables on each side (connecting the tailgate to the bed) like every truck ever made. A 1/2" socket on a drill was needed. Then (as another thread re: removing the entire tailgate here mentions), you really gotta tug on the passenger side hinge at a 45-degree angle... and keep tugging until it pops out. I'm glad the whole unit is built tough but damn. 4+ hours to install a tailgate LED bar. 30 minutes for wiring/soldering/electrical tape... 3 hours for that damned tailgate... and 30 minutes for lunch.
Here's the light bar I chose to install... looks fantastic:
https://www.amazon.com/gp/product/B0771WDRHH/
60" with red sequential turn signals and super bright white reverse lights.