It is generally much better to use a dedicated manual trans fluid in a tranny like yours.
Why? Better gear and bearing protection, for sure. Better shifting is almost a given.
But then why do they spec ATF? It's cheap, one fluid at the dealer for PS systems, transfer cases, auto trannys and manual trannys.
And a very important consideration is cold shifting complaints from customers.
There are indeed some special manual transmission that should use ATF, but yours is not one of them.
Redline MTL or Amsoil MTF would be a big upgrade for you.