If you went to a participating KFC yesterday for your free "piece" of grilled chicken, you were probably expecting a drumstick, thigh, breast, etc. - i.e., what we normally think of (and KFC refers to on its menu) as a "piece." Instead, you got this. They probably should have described it as a "sample."
Well, you get what you pay for, I guess. The interesting part is that many commenters reported that their KFC restaurants used fairly shady bait-and-switch tactics to avoid the promotion (claiming it would take 20 minutes to make a batch, insisting that a purchase was required even though the KFC website says it's not, etc.). Another example of Corporate deciding that a giveaway promotion would be awesome, then passing the buck on to the individual franchisees?