I face the same issue in version 5.4.0. I have raised a feature request.
It would be very helpful if this gets resolved.
The workaround I use for this issue is following:
The advantage is that you can distinguish the interfaces between each other. However, you need to be careful and avoid updating the interface, in such a case the interface name would get renamed back to the binding name from the WSDL.
This approach is especially helpful when you need to test or mock multiple versions of the same service within the same SoapUI project.