Reflex will (in theory) allow flex from front to back, its the 2 bolt fixing system that is the channel that allows heel lift. I notice it a lot when riding my burton channel board. I notice no flex from the reflex disc.
The tech they talk about doesnt flex, and the tech they dont talk about flexes a lot.
I believe its just a messed up transition period for burton these last few years, they are torn between justifying their world domination strategy and actually making stuff that works well.
This period of burton technology will probably be looked back at with a chuckle in 10 years time, but they do try new shit you cant deny that.