LOOPBACK does not work for portable java pipelines

org.apache.beam.vendor.grpc.v1p26p0.io.grpc.StatusRuntimeException: UNIMPLEMENTED: Method org.apache.beam.model.fn_execution.v1.BeamFnExternalWorkerPool/StopWorker is unimplemented
        at org.apache.beam.vendor.grpc.v1p26p0.io.grpc.stub.ClientCalls.toStatusRuntimeException(ClientCalls.java:240)
        at org.apache.beam.vendor.grpc.v1p26p0.io.grpc.stub.ClientCalls.getUnchecked(ClientCalls.java:221)
        at org.apache.beam.vendor.grpc.v1p26p0.io.grpc.stub.ClientCalls.blockingUnaryCall(ClientCalls.java:140)
        at org.apache.beam.model.fnexecution.v1.BeamFnExternalWorkerPoolGrpc$BeamFnExternalWorkerPoolBlockingStub.stopWorker(BeamFnExternalWorkerPoolGrpc.java:247)
        at org.apache.beam.runners.fnexecution.environment.ExternalEnvironmentFactory$1.close(ExternalEnvironmentFactory.java:159)
        at org.apache.beam.runners.fnexecution.control.DefaultJobBundleFactory$WrappedSdkHarnessClient.$closeResource(DefaultJobBundleFactory.java:642)
        at org.apache.beam.runners.fnexecution.control.DefaultJobBundleFactory$WrappedSdkHarnessClient.close(DefaultJobBundleFactory.java:642)
        at org.apache.beam.runners.fnexecution.control.DefaultJobBundleFactory$WrappedSdkHarnessClient.unref(DefaultJobBundleFactory.java:658)
        at org.apache.beam.runners.fnexecution.control.DefaultJobBundleFactory$WrappedSdkHarnessClient.access$400(DefaultJobBundleFactory.java:589)
        at org.apache.beam.runners.fnexecution.control.DefaultJobBundleFactory.lambda$createEnvironmentCaches$3(DefaultJobBundleFactory.java:212)
        at org.apache.beam.vendor.guava.v26_0_jre.com.google.common.cache.LocalCache.processPendingNotifications(LocalCache.java:1809)
        at org.apache.beam.vendor.guava.v26_0_jre.com.google.common.cache.LocalCache$Segment.runUnlockedCleanup(LocalCache.java:3462)
        at org.apache.beam.vendor.guava.v26_0_jre.com.google.common.cache.LocalCache$Segment.postWriteCleanup(LocalCache.java:3438)
        at org.apache.beam.vendor.guava.v26_0_jre.com.google.common.cache.LocalCache$Segment.clear(LocalCache.java:3215)
        at org.apache.beam.vendor.guava.v26_0_jre.com.google.common.cache.LocalCache.clear(LocalCache.java:4270)
        at org.apache.beam.vendor.guava.v26_0_jre.com.google.common.cache.LocalCache$LocalManualCache.invalidateAll(LocalCache.java:4909)
        at org.apache.beam.runners.fnexecution.control.DefaultJobBundleFactory.close(DefaultJobBundleFactory.java:319)
        at org.apache.beam.runners.fnexecution.control.DefaultExecutableStageContext.close(DefaultExecutableStageContext.java:43)
        at org.apache.beam.runners.fnexecution.control.ReferenceCountingExecutableStageContextFactory$WrappedContext.closeActual(ReferenceCountingExecutableStageContextFactory.java:212)
        at org.apache.beam.runners.fnexecution.control.ReferenceCountingExecutableStageContextFactory$WrappedContext.access$200(ReferenceCountingExecutableStageContextFactory.java:188)
        at org.apache.beam.runners.fnexecution.control.ReferenceCountingExecutableStageContextFactory.release(ReferenceCountingExecutableStageContextFactory.java:177)
        at org.apache.beam.runners.fnexecution.control.ReferenceCountingExecutableStageContextFactory.scheduleRelease(ReferenceCountingExecutableStageContextFactory.java:136)
        at org.apache.beam.runners.fnexecution.control.ReferenceCountingExecutableStageContextFactory.access$300(ReferenceCountingExecutableStageContextFactory.java:48)
        at org.apache.beam.runners.fnexecution.control.ReferenceCountingExecutableStageContextFactory$WrappedContext.close(ReferenceCountingExecutableStageContextFactory.java:208)