The first Fluid Drives that Chrysler made not only used motor oil but it used the same oil as the engine it was attached to, they shared the oil.

While the Fluid Drive wasn't an automatic, per se, it did have a torque converter and other features present in what we call an automatic.

As for switching from gear oil to ATF in a stick, that was done to ease shifting, NOT for durability.

They say there are no such thing as a stupid question.
They say there is always the exception that proves the rule.
Don't be the exception.