APH do need a lot of insects, it should make at least half their diet. Actually the more insects make up of their diet the less their poo smells.
But APH dont have the abilty to store the fat, like other hedgehogs that do hibernate. So the APH will just gain weight, and become overweight where as a wild hedgehog will store it ready for when they hibernate in winter.
If we take how much each should weigh an APH should weigh 300g-600g to be healthy. Where as a wild hedgehog should be at least 600g especially before hibernation otherwise they die in hibernation.
So ideally hedgehogs need more low fat insects in their diet. The cat biscuit is mainly there to pick up neutrients they need to stop them becoming neutrient deficient.