One handed BH's are good on grass because you have more variety and racquet head speed with the shot, and the ability to hit low shots and still get the ball on the sweet spot of the racquet.
You're good at memorising statistics, players and the like of the ATP tour but as for your understanding of the technical side of the game and biomechanics and what not...
How do you have more variety? Because single handed players sometimes
have better slices?
And you don't automatically get more racket head speed with a single handed backhand, you can however achieve further extension on the follow through to maximise power.
And the ability to use your non-dominant hand in low shots is actually very important in hitting low balls because it enables you to create further whip of the wrist to allow for more top spin, which is crucial on low balls. This allows you to balance out the power through both both arms where as if you're a one handed player, you have to create the whip and power with a single arm which is extremely strenuous on your wrist and rotator cuff. Easier control is far more achievable with a double handed backhand in today's gruelling game, when you may have to hit 5 or more backhands in every third rally in a best of 5 set match. It takes its toll.
And I don't know where to even begin with the sweet spot part, since when did using two hands disable you from achieving a central contact?