The moment B asked for advice, the hole was over. It makes no difference if Player A's statement was misleading. He offered advice and is penalized two strokes. Factual information which is available to all players on the score card, tee signs, etc., is not defined as advice. Information obtained by observation is not defined as advice.
Observation is one thing, but a physical act, such as moving the towel, is a violation.
Player B is penalized two-strokes. This is a fooler. It seems like they both should be penalized. Player B's round was over and Player A's round had not yet begun. Jon Ebert, a golf consultant and teaching professional, writes for Naples Daily News in Florida.