I think the idea is transmissions are much more complex than earlier designs therefore a more improved better by design fluid is required. Not just hydraulic controls, internal electrical controls.
It's easier and covers all potential fluid mistakes by sticking to a guidance of " Power steering fluid only usage ". There is logic in " keep it simple ".
A power steering pump is just belt driven hydraulic pump. Not a lot of complex materials or parts. The fluid is not a complex mix of additives for operation.
Transmission fluid has all kinds of additives for shears, foaming , temp, dissimilar metals, friction materials, lubrication. I would use ATF in both, but I wouldn't use power steering fluid in transmission. ( Unless in some mad scientist experiment.)
It's easier and covers all potential fluid mistakes by sticking to a guidance of " Power steering fluid only usage ". There is logic in " keep it simple ".
A power steering pump is just belt driven hydraulic pump. Not a lot of complex materials or parts. The fluid is not a complex mix of additives for operation.
Transmission fluid has all kinds of additives for shears, foaming , temp, dissimilar metals, friction materials, lubrication. I would use ATF in both, but I wouldn't use power steering fluid in transmission. ( Unless in some mad scientist experiment.)