Service user has Lync and Hosted Exchange service assigned.
When the Lync license is released, the user stays in Lync, with removed
If there is no Exchange service assigned with the user then the 'Release License' button removes the Lync user from the Lync server.
Is this intended behaviour?
This is expected behavior of the Lync provisioning.
When Lync service is removed from service user, APS Application just disables the Lync service, leaving the user in system.
However, if Lync was the only or last Active Directory service on this user, the user will be removed from AD, which causing user removal from Lync servers.