Why can returning a new object from a custom BeanPostProcessor silently remove @Transactional, @Cacheable, and @Secured proxies?

If postProcessAfterInitialization returns a brand-new object instead of the (possibly already-proxied) bean it was given, any AOP proxy Spring built for that bean is discarded — silently disabling every annotation-driven feature (transactions, caching, security) that depended on that proxy.