I don't see how they are much different than the CJ Scamper cactus saddles were. A dealer said you can get them in any of their current trees, it just leaves the space in the back. I'm sure there has to be more to it? But thus far it honestly doesn't sound revolutionary.
I also noticed you asked about the flex trees, which I don't have experience with. FC Saddlery and tack has sold a few they may be able to tell you more about them and how the customers are liking them.