The "Add a new template to all docker clouds" build step makes an excellent follow-on build step to the "Build / Publish Docker Containers" build step.
e.g. you can create an image tagged as myregistry:1234/myimage:version-${BUILD_NUMBER} and you'll get myimage:version-1, myimage:version-2 etc pushed to your registry in subsequent builds.
However, if you use the "Add a new template to all docker clouds" build step and specify a "Docker Image" field of "myregistry:1234/myimage:version-${BUILD_NUMBER}" then that's exactly what you'll get - it won't replace ${BUILD_NUMBER} with the build number.

What should happen is that all of the plain-text fields should be subjected to Jenkins' variable substitution so that all text fields can be parameterised.