The distinction between "possession" and "ownership" is just "renting" or "borrowing". Virtually everyone has rented or borrowed something before -- an apartment, a car, a pencil from their schoolmate. I don't see why cleaving this distinction would not be a "winnable battle" given that everyone has first-hand understanding of it.

Actually, someone had tested the "more light" hypothesis by the time you were looking for results, and had written about it! https://meaningness.com/metablog/sad-light-lumens