Sorry, but this is nonsense. First of all, most decent RDs have plenty of turns on the idler cage spring. So the change in tension from the small arc of deflection is fairly small. But the real key is that lower loop tension is near zero compared to the upper tension which is what propels the bike.

Pull the lower loop forward and there's probably a pound or two of tension involved (regardless of gear). Now compare to the upper loop tension driving the bike which can easily run up into hundreds of pounds. (pedal force / crank length X chainring radius)

As I said earlier, larger sprockets mean lower chain tension for any given torque transmission.