I'm skeptical about it too. He looks pretty hairy in Zardoz as I remember it.Baloney.Supposedly, Sean Connery wore a chest hairpiece as James Bond, because someone didn't think his natural chest hair looked virile enough or something.There are so many pictures of shirtless Connery pre and post Bond to prove the lie to that idea.
I've seen Shatner in television appearances before Trek, notably in Man from UNCLE, and his hairstyle looks the same, but UNCLE was at least a year or two before the studio was buying custom hairpieces for him. They must have been going through his own stylist.