KEF LS50 Meta

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. 

This really changes the game BIG TIME for box speakers now !..

Not really. The KEF is still a box speaker.