If I do a production build with gradle clean build -Pvaadin.productionMode and then run gradle jibDockerBuild --image localhost:5001/my-test, I get a container image that executes the application in production mode.
If I do a gradle clean and then invoke jibDockerBuild it builds an image for an application running in development. This is expected because vaadinBuildFrontend has not been executed.
If I run ./gradlew vaadinBuildFrontend jibDockerBuild --image localhost:5001/my-test -Pvaadin.productionMode, again I get an image that runs the application in production mode.