No.
It's an inarguable fact that Minoxidil works by blocking the production of collagen, thinning hair and scalps have an excess of collagen. Collagen is also responsible for cell regeneration in skin, youthful appearing skin, and combating the effects of aging
Putting Minoxidil on your face to have a fuller beard is completely stupid. You have to use it forever to keep your beard gains, and it's constantly aging your face, destroying the natural and necessary collagen that your face needs to not look like it caught on fire and someone tried to put it out with a screwdriver.
Not only that, Minoxidil causes facial bloat. Extreme facial bloat. If he didn't have a beard and just put it on clean shaven he would notice way more puffiness on his face compared to when he didn't put it on his face.
Minoxidil isnt marketed for anything other that use on your scalp for good reason.