The "pattern" common to cases of "male pattern baldness" is pretty much limited to the scalp. I don't have any definitive medical literature to cite, but I have observed many guys with thick full beards and bald heads. And I'm not talking about shaven heads, I mean real regular age-related baldness

For most fellows, beard hair seems to remain darker than head-hair as the graying process gets underway. In my own case, the pubes are turning gray even more slowly ~ dark hair down under, "salt & pepper" facial hair, almost-all-gray on top.

My facial hair is thinner than it once was, and almost-bald in spots, but that's due to radiation treatment, not age.