However I thought the more recent matt finishes had more to do with IR
attenuation, so why the gloss?
I also understood that the matt "barley grey" finish was to prevent the reflection of IR energy. I was also told that when the E-3D entered service, the request to paint it matt (rather than the shiny grey/white of the NATO/USAF fleet) caused some consternation at Boeing because the new paint scheme would also absorb heat from the sun whereas the old shceme would reflect it. The story was told that when the USAF transport fleet changed from gloss to camouflage, there was an increased failure rate of aircraft systems due to insufficient cooling. The result was a somewhat expensive investigation as to whether the E-3D's new scheme would affect the mission system or would additional cooling be needed.
Perhaps the Sentinel systems got a little warm?