I don’t think you are correct. Your statement violates the law of conservation of energy.
While the watts produced by the generator may be more than the system can use or store, the watts quantity transmitted through the belt to the alternator is greater by a significant margin. A 60 % effieiency would be good, meaning that there is a 40% loss.
The part of my post above the asterisks was a recap of what was said by Rick.Donaldson , I do not endorse his evaluation.