As of meb-3.12.0, the cloud options take precedence, i.e. specifying any of the "--cloud-*" options makes MEB treat it as a cloud operation.
The backup file name to be used on the cloud is to be specified by a "--cloud-" option. Any value represented by "--backup-image=<value>" is not interpreted by MEB(in case of cloud operations), and the above commands would work correctly as expected.
I agree, this dependency on the unused option of "--backup-image=<value>" can be done away with, if possible and thanks a lot for pointing it.