While in the process of swapping the trans in my miata, I noticed the 6 speed turret does not contain gear oil but instead has grease on the shifter assembly, and a hole in the turret that drains down to what looks like the output shaft.

Since this hole is here, Couldn't I just fill my tranny through the turret?

So to fill the trans all I would need to do is remove the fill plug, pour trans fluid into the turret, and wait for it to come out of the fill plug? Or is the oil by the output shaft sealed off from the main case?