I will agree with you that without room correction, SPL (volume) increases. And when a speaker is louder, it sounds better to us smile Also room correction can make highs sound bad. There can be other deleterious effects also.

So look beyond just volume. Your room may be perfect and not need any correction. I can't say the same for my room. Audyssey XT32 worked magic.

Now for Bryston to say that if the design is sound they don't need to be corrected, speaks volumes about how much they need to learn about the system comprised of the speakers, the room and the brain/ears. A better designed speaker will sound better though in a bad room than a poorly designed speaker for sure.

House of the Rising Sone
Out in the mid or far field
Linearity and mid-woofers are over-rated