I did not consider the KEF Reference for my speaker upgrade because they ideally need to be placed a bit away from the front wall. It would be great if this Meta stuff makes placement of the Reference and even Blade more flexible.

A couple of other speakers that use this back wave canceling idea is of course Vivid (B&W) and Yamaha NS 5000. KEF seems to think their new way of doing this is better.
Kef has found the way to get a much BIGGER improvement using this technology than these other companies have ! This really changes the game BIG TIME for box speakers now !..

Here’s a review on these improved Kef speakers

https://www.lite-magazin.de/2020/09/kef-ls50-meta-klarster-klang-durch-verwandeltes-material/ 

 I can't wait to hear Kef's bigger speakers with this technology !!  Coming SOON !
This really changes the game BIG TIME for box speakers now !..
Not really. The KEF is still a box speaker. 
Absorbing most of the backwave as advertised sounds really good, but would like to see some tests to confirm the effectiveness

I dont know where you read that it absorbs most of the backwave. It does not. The absorber is only used on the tweeter. Not the woofer. 
kenjit

Steve Guttenberg said these Meta’s sound like Open Baffle speakers and that’s a real.. game-changer for Box Speakers...

The best of both worlds !

https://www.youtube.com/watch?v=oKTYvP7YQ0Q&t
 
 I can't wait to hear the Kef R11's with this new Technology !