Ghost doesn't win board battles because he generally avoids them, one reason you pair him with someone like Braun.
His hit rate is less than half that of any other defenseman, no, he's not nearly that elusive.
Provorov is great at anticipating the hit and getting the puck out then dodging the forechecker, and he still gets hit at twice the rate as Ghost.
Giroux also tends to play on the edge, one problem he has at center (and probably the reason they don't want to rush Frost) is he has to make plays on defense around the net in AV's system, and he's physically over matched at time, even though he's significantly stronger than Ghost. Which is a good reason to move him back to wing sooner than later, to reduce that kind of punishment.