I don't think proof either way actually exists yet. The supposed main "benefit" is venous return from the extremities (that is to you and me - blood going from the legs back to the heart) so there is a bit of a common sense notion there.
Yet, venous return is something you can aid yourself via post exercise stretching with as low a COG as possible. Some people may struggle with that, particularly if you have had/are prone to varicose veins/DVT or CVD/I.(all relative to vein walls and pooling of blood)