Does it provide any heat-reduction benefit?

Yes, this film does indeed offer heat blocking ability as well (up to 65%) if installed correctly - on the exterior, with the white side facing out. The black/glue side would then be facing the interior. Here is the spec sheet so you can see the percentages: https://www.decorativefilm.com/mm5/graphics/00000001/SX-1940%20One%20Way.pdf