The expression “two grounds of inclusion” identifies two specific reasons why separate things are brought under the common meaning. Calling both face and heart “fire” gathers them; identifying light for the face and heat for the heart differentiates them.
If we merely say “face and heart are both fire,” the shared designation is present, but separate grounds have not been stated. If we remove the shared figure altogether, the defining unity also disappears.
The diagnostic question is: What is the common meaning, and by which distinct aspects does each referent enter it?