My understanding is that the bevel box itself is not particularly noisy. It is resonance and amplification by the panel behind the seats which causes the problem. This is also why it's typically most evident at a specific range of road speeds (in my case 60 - 65mph). If it were down to assembly tolerances I would expect it to be noisier over a much wider speed range.
The NVH mod for pre 2014 is supposed to improve this and 2014 onwards cars have this flexible mounting as standard.
Bear in mind that a worn alloy rear sprocket will scream and could be mistaken for BB noise. This is a separate issue cured by a steel or supermax upgrade.
I'll set up a survey to see if this is born out in practice.
