[nova] [cinder] [ceph] Questioning deployment choices

Hi Fellow OpenStackers! I have a question regarding nova-cinder-ceph deployment configuration. Most notably ephemeral storage. So - if I configure Nova to use Ceph as ephemeral storage and Cinder's only backend is Ceph as well then how does ephemeral storage differ from persistent storage now except for interface from Cinder rather than Nova (and all that comes with that) and a different pool? Was Nova's Ceph integration added just to be able to avoid Cinder in certain scenarios? Other Cinder backends did not get support from Nova. Looking forward to your insights. -yoctozepto