Perhaps less aluminum is removed from the headphone that doesn’t have the batteries. That would offset the weight.
Apple is using a braided copper coil in the charger. I believe they are the only ones doing this.
Also, this confirms that the Mac Pro is using PCIe Gen 4, which is great!
Where is the PSU in the final shot? Can you post more pics of the PSU? It looks like it’s dually cooled from both the bottom front fan and the blower on the back.
Very weird. Is it possible that Apple repair techs use an adhesive dissolving solution? Would make the repair “easy” for them while keeping the batteries solidly in place.