EJB 3.0 Specification 3.4.5.2:

"All business object references of the same interface type for the same stateless session bean have the same object identity, which is assigned by the container.
...
Session bean references to either different business interface types or different session beans will not be equal."

The SessionProxyInvocationHandlerBase.invokeEquals() however doesn't take into account the business interface type of the proxies and thus violates this contract.