yes there is.
if the later flow-the flow that bees would use as winter stores, well if that flow comes from a nectar source that is somewhat full of solids, then you have a good reason to extraxt twice. if the bees go into winter with honey that is full of solids-honeydew honey or others, don't know all of them the chances of them going throu winter get thinner by the pound of that honey :-D. also, if they get honeybound in late summer they might swarm, and a swarm that late....has little chances, not to mention the primary colony.