AbstractAutowireCapableBeanFactory#doCreateBean 调用 getSingleton不理解

原代码是
`if (beanDefinition.isSingleton()) {
//如果有代理对象，此处获取代理对象
exposedObject = getSingleton(beanName);
addSingleton(beanName, exposedObject);
}`
spring已经在 initializeBean后 bean 不是已经被替换为 代理对象了吗，如果这里再调用getSingleton 方法，就会再生成一个新的代理对象。这段逻辑不理解

Start with AbstractAutowireCapableBeanFactory#doCreateBean and trace initializeBean, getSingleton, and addSingleton to assess the reported concern about creating a second proxy. The issue names no failing test or agreed change; first establish whether this is a defect or a request for explanation. Completion requires resolving that distinction and confirming the expected singleton proxy behavior.

Written by the indexing model from the issue text.