This joint makes more sense when you have multiple joint segments. _3 is the last joint aligned to that limb, and the final segment in the twist. And the end joint has (sometimes? always?) a different orientation, and can be used as an attach point for other things.
If you want to get rid of that extra joint, you could just try making a post Python script. Reparent the End joint, and delete the one you don’t want.
The skin joints should be separated from the rig nodes. So it shouldn’t break anything.
import pymel.core as pm
for side in 'LR':
endJoint = pm.PyNode(side + '_hindLeg_End')
lastJoint = pm.PyNode(side + '_hindLeg_3')
pm.parent(endJoint, lastJoint.getParent())
pm.delete(lastJoint)
(I hand typed this and didn’t test it.)
(If you do really want to edit the components, I recommend cloning them as unique custom components. This way, you won’t overwrite your changes when you upgrade mGear.)