YES, it is true. Refer Para 7.6.3 Missed ejbRemove() calls from ejb specs:
The Bean Provider cannot assume that the Container will always invoke the ejbRemove() method on a session bean instance. The following scenarios result in ejbRemove() not being called on an instance: • A crash of the EJB Container. • A system exception thrown from the instance’s method to the Container. • A timeout of client inactivity while the instance is in the passive state. The timeout is speci-fied by the Deployer in an EJB Container implementation specific way.