libxmlb1 security update: "No changes rebuild"

[flynn16 at tutanota.com]

Dear maintainers:

The changelog of libxmlb1 0.1.8-1~ubuntu18.04.2 came to my attention. It says

libxmlb (0.1.8-1~ubuntu18.04.2) bionic-security; urgency=medium  * No changes rebuildDate: 2020-06-09 18:12:15.680810+00:00Changed-By: [email address hidden] (Leonidas S. Barbosa)

In Debian ( https://tests.reproducible-builds.org/debian/rb-pkg/unstable/amd64/libxmlb.html ) this package is regarded as "reproducible", which makes me more confused. If the package has no changes in the source code, what is the reason for the rebuild, and why is it published as a security update?

Best Regards,
Flynn