Definitely not. If you look closely, you can clearly see the striations in the muscles which is something never seen (to my knowledge anyway), in a muscle that has a covering of synthol. Added to that, the synthol would have had to be a master craftsman to have been able to sculpt such an aesthetic and perfectly formed set of muscles.
Anyone saying that this is synthol based is either misguided or, more likely, just jealous of the amount of hard work and suffering that has gone in to the guy developing these awesome legs.