Found a NOS MTF2 5L jug which should last a LONG time- can't argue with what has worked and it gets expensive trying out notchy fluids- Honda MT2 doesn't last X2, GM Synchromesh, and another. In a cold climate this oil just plain works well.
I have a 2019 Miata. At one time the Miata MT gear oil was thinner but presently is 75w90. The interesting ingredient is moly. My guess is the moly is not bonded with sulphur like used in motor oil.