有耦合或解耦束吗？

Question

与抽象类和接口定义关系的documentation说：

    With the **ResolveTargetEntityListener**, you are able to decouple your bundles, 
keeping them usable by themselves, 
    but still being able to define relationships between different objects

但是我在示例中看到customer中位于AppBundle的{​​{1}}实体已经取决于位于InvoiceSubjectInterface的{​​{1}}。所以AppBundle和InvoiceBundle没有分离。

有人可以向我解释这两个捆绑包是如何在文档中注明的那样解耦的吗？