i do not think they do that on purpose to prevent us to play copies. if the purpose was so, they would prevent us to play even BD-R dual layer discs, or even single one discs. each standalone player can indentify burned discs as each manufacturers of BD media put a code on them. on many countries there is laws that authorize copies. i think the purpose is more economical or physical, maybe the ub900 has a more efficient lazer to penetrate more layers with different sizes that all. they simply want to do more benefits with putting only good quality lazers, not excellent ones ! the price does not matter for me, but they want to screw us, by putting new models that are expensive and worse than the formers one. it makes me mad if oneday you are aware of new 2021 model that can read bd-xl disc, i will be glad of your help in this thread. maybe the new Playstastion 5 can read bd-xl discs ? who knows ?