Not sure about other transmissions, but Toyota used a modified ATF iin the Getrag 6-speed (twin-turbo Supra) and way before that we used Dexron in Corolla 5-speed manual trans (around 1984-85). That was the Front Wheel Drive model, by the way. The trans seemed to hold up just fine.
We used to run ATF in rear wheel drive manual trans, for high altitude (super cold) winter operation. It was the only way to get out of 1st and into 2nd when you had to leave the driveway and head uphill! If you couldn't make the shift (with gear oil), you couldn't get back into 1st without stopping, and once stopped on the snow....you couldn't get going again!
I run 1/2 and 1/2 in my street roadster and it's been fine for 2 years.... and it shifts great!
Regards, JimL