Hi Sean,
On the X460-G2-10G, the front 10G ports are used for alternate stacking (to allow alternate stacking without requiring the VIM-2x).
On the X460-G2-1G (without built-in 10G ports), the VIM-2x is needed for alternate stacking.
Unfortunately, there isn't a way to use the VIM-2x ports for alternate stacking on the 10G version of the X460-G2.