What is the meaning behind the designer's statement that while most other AOP supports circle reference, the spring @Async does not?

edit

The designer's statement means that, in most other Asynchronous Operation Processing (AOP) frameworks, circular references between methods are supported. However, with Spring's @Async, circular references are not supported. This means that if a method A calls method B and method B calls method A, and both methods are annotated with @Async, it will result in an error in Spring's @Async but not in other AOP frameworks.