i have this character with multiple facial hair components. as been seen in the screenshot.
i export it as a unity template, and enabled "merge brows and beard into one object."
when i open the fbx in 3d software ( in my case cinema 4d) i see that there alot of blendshapes in the facial hair object. (in this case 455)

what happens is that the 3d models are merged, but not the blendshapes.
so there is still a separate set of blendshapes for the brows, side burns, etc.

would be nice if those blendshapes are also merged.