In my personal experience (and in the FLIR application guides) the main factor affecting paint emissivity is the glossiness (matte paint is much more emissive). I would have liked to see that test done with matte white paint, or at least have them mention that factor. From the video it was hard to tell, he said super bright Rustoleum, which isn't the same as matte. I would imagine emissivity to be more important that reflectivity given the result with aluminum (super reflective but still got super hot due to the extremely low emissivity).

I like the use of the thermocouples, but unfortunately it didn't go quite far enough...