In part because Chanel may have started using inferior caviar and stopped 18k or 22k gold plating the CC, they can justify double-flapping the jumbo and maxis; it is afterall added material and labor costs to add the flap. My 2008 single flap jumbo is sturdy and rigid no matter how much weight I carry.
I have not bought new since 2008 but all the news tells me that Chanel is quite dissappointing lately.