Heres the thing big homie.
People go by what the manga says, or what the manga infers, the manga infered that you needed both of the uchiha specs to get the sasunoo, sasunoo was the manifistation of both of the uchiha god specs. But, if it happens to be contridicted later in the manga then so be it, that just means that its not needed. It is infered that you need a lot of chakra to do Sage mode, So we know that Jariya, Naruto, and Minato all have alot of chakra based on that, but until a chapter is released and the person using FROG sage mode is stated to have a small chakra reserve, i will continue to believe that people with sage mode have large chakra supplies.