Jon Jones has skinny thighs as well. His entire leg is skinny and he is naturally thin boned. Skinny thighs and calves are more vulnerable to attacks through kicks than muscular thighs and calves that can resist them. Muscular thighs form a barrier to protect the bone underneath. I don't buy the hype of his squating strength when his thighs don't look muscular at all either as all of the video footage I have seen of him squatting is doing those half-squats where there are bars that stop his squats half way through with 3 or 4 plates on each side. He also usually does not put the bar across his shoulder, but instead holds the bar in his arms while doing squats. That also reduces the difficulty in going down in squats. Also, having skinny legs makes the center of gravity much higher (as Jon Jones has a pot belly where he a good part of 40 lbs).
While he does not have to worry about being taken down by Gane, Jones is more vulnerable to takedowns at heavyweight by other strong competitors who have really good wrestling. Skinny legs are also easier to get a hold of during a takedown than tree trunk legs that will have more "counter weight" and harder to wrap the arms around.
Put it altogether. Gane weighs the same as Jones at 250 lbs. However, Gane looks a lot bigger and with a completely balanced physique top to bottom. Both have similar height. What does that say? Gane is naturally a bigger competitor with bigger bones and muscular frame. I am not saying Gane is going to beat Jones. Just saying he has the natural advantage has he is the bigger, more muscular and more thick boned competitor.
Come on! Larry wheels is like Arnold. Tall and has proportionally smaller legs than his upper body, but his legs are still damn huge. No one can call these legs "skinny". Jon Jones has skinny thighs with no muscles or anything on them. Completely different.