gsutil mv not working as expected

$ take /tmp/gsutil_mv
$ mkdir test_data
$ echo "test_data" > test_data/text.txt
$ mkdir test_data_b
$ echo "test_data_b" > test_data_b/text.txt
$ gsutil ls gs://my-organization-empty-bucket
$ gsutil cp -r test_data gs://my-organization-empty-bucket
Copying file://test_data/text.txt [Content-Type=text/plain]...
- [1 files][   10.0 B/   10.0 B]
Operation completed over 1 objects/10.0 B.
$ gsutil ls gs://my-organization-empty-bucket
gs://my-organization-empty-bucket/test_data/
$ gsutil ls gs://my-organization-empty-bucket/test_data
gs://my-organization-empty-bucket/test_data/text.txt
$ gsutil rm -r gs://my-organization-empty-bucket/test_data
Removing gs://my-organization-empty-bucket/test_data/text.txt#1534770322877415...
/ [1 objects]
Operation completed over 1 objects.
$ gsutil cp -r test_data_b gs://my-organization-empty-bucket
Copying file://test_data_b/text.txt [Content-Type=text/plain]...
/ [1 files][   12.0 B/   12.0 B]
Operation completed over 1 objects/12.0 B.
$ gsutil ls gs://my-organization-empty-bucket/
gs://my-organization-empty-bucket/test_data_b/
$ gsutil ls gs://my-organization-empty-bucket/test_data_b
gs://my-organization-empty-bucket/test_data_b/text.txt
$ gsutil mv gs://my-organization-empty-bucket/test_data_b gs://my-organization-empty-bucket/test_data
Copying gs://my-organization-empty-bucket/test_data_b/text.txt [Content-Type=text/plain]...
Removing gs://my-organization-empty-bucket/test_data_b/text.txt...
Operation completed over 1 objects/12.0 B.
$ gsutil ls gs://my-organization-empty-bucket/
gs://my-organization-empty-bucket/test_data/
$ gsutil ls gs://my-organization-empty-bucket/test_data
gs://my-organization-empty-bucket/test_data/test_data_b/
$ gsutil ls gs://my-organization-empty-bucket/test_data/test_data_b
gs://my-organization-empty-bucket/test_data/test_data_b/text.txt