The differential gear system (i.e. bracket + bevel gears) provided by VEX IS 1 input. Admittedly, the bracket is cumbersome and the directions of the outputs might not be how the users want it. But it is 1 input (that sticked close to the original design and intent of differential).
I believe the mechanism that mentioned by 5062F_Adam was modelled or adapted from this - Differential Drive/Tilter Mechanism - VEX V5 General Discussion - VEX Forum.
And looking at it again, I suspect I know why the “confusing” or conflicting views that we have - using this specific setup, then yes - you are right that it will need 2 motors in order for the power-sharing ability of differential to work.
But if you are looking at the other possible differential setup (eg. the differential system by VEX), it is not a must to have 2 motors to have the power-sharing ability.
And honestly, the need to have 2 motors to power-share to 2 outputs defeat the purpose of power-sharing in the 1st place, unless the torque required is too much for 1 motor.
And the above are my 2 main points.
Anyway… I don’t see any more value-added in replying to this thread anymore.
I have already provided my viewpoints.