Originally Posted by
Falchoon
I believe Di2 for MTB already has a sort of automatic shifting on the rear, when you change down on the front the rear automatically changes up a gear or two.
This is based on a totally different premise. It is hybrid of sequential shifting, not really automated shifting. It's is a mode to make the transition from one gear ratio to the next more even in certain situations.
Shimano Synchronized Shift puts all the control into one shifter instead of two.