It does scale to zero CPU when your application isn’t serving requests. See the pricing model at https://aws.amazon.com/apprunner/pricing/ for more details. It does not scale to zero memory, however, because customers have told us that cold-start latency has been their biggest pain point with Lambda functions. App Runner containers can respond to requests in milliseconds as a result.
Most of the stuff my company is running is made up of data pipelines and machine learning pipelines. So we have a lot of infrequent jobs that don't really care about latency.