Kenjit
I very much enjoy your posts, they are a visible display of the "buy in" to the marketing effort called "specs". You are a real life Don Quixote!
You realize that manufacturers invest in published measurements to establish their marketability/salability (not their real performance). Any kind of acoustical measurements are relevant only to the space they are taken in, in the conditions they are taken. I guarantee you that any space you use would not be similar to their space, making their specs meaningless to anything other than comparing their product to each other.
Brad