I wasn’t speaking per se of furled leaders but rather of leaders in general. Thickness, be the leader furled, mono or FC, equates to more leader surface for the water to act or to drag upon. As for them being more flexible, it depends! 
John…
What reduction factor do you furl to? If it is the more or less ‘standard’ 10%; go to 20% and see the difference it makes! I have a couple that I furled to at least 30%, just for grins, and they are as stiff as a brand new lariat!
Frank