That sounds like a cannondale issue rather than BB30.
Exactly, one example is the brake cable/housing having too much friction due to poor installation, blindingly obvious when you have Trek next to it that felt butterly smooth, no matter which levers.
Put it this way, every Cannondale bicycles with BB30 we used to sell in my old shop always get returned to stop it creaking.
We very rarely have problem with Trek road bicycle because they were build extremely well in the first place.