bba comes from CO2 problems, yes. but whether it can be a sign of CO2 flux, or overall insufficiency, i cant say; probably both induce it equally well.
That's just way to general a statement IMO. If that was true, every tank without CO2 would have BBA and that's not the case. What every tank has is organic waste and this needs to be kept in check especially if the plant uptake isn't there.