So does that mean Google should not even experiment with the idea, just because nobody else has published data about it yet? Why does there need to be "proof"? It is Google's choice, just like it is your choice to use Google products.
It's when they parade out the idea that "real names = better quality" as the reason for a change - without citing it. Especially since it's such a cross-product change that effects literally every single one of their products.