I appreciate this info is difficult to find (!), but for a bunch of
historical reasons, there are actually a different set of variations
tested when we test sid compared to when we test bookworm. In other
words, the differences between the two builds is not just the package
version and Debian distribution.
We try to canonically document the differences on this page:
https://tests.reproducible-builds.org/debian/index_variations.html
And almost certainly the difference is down to the build path. :)