The bb is quaife. Need I say more.
They get hot because all bb's are only 95% efficient. Its part of the drop from 115 bhp at crank to 80 bhp at the drive wheel.
5% of 30 horsepower (when cruising at 60mph) equals around 1kw of heat. Constantly. Even under engine breaking. More during hard acceleration.
There is no drop of 35hp in the transmission. The figures are arbitrary and meaningless.
All gearboxes get hot but that's not the issue. The bevel boxes are failing and having to be replaced. That's the issue.
Charles makes a good point and regardless of the actual figures his calculation gives a good order of magnitude for the heat generation.
It's never going to run cool so the question should be whether the oil used is suitable for sustained running at the operating temp.
My late 2013 BB is acceptable so I think it is OK.
Just off to touch some wood now
