I noticed a little weirdness when uploading a package for multiple
suites, in my case for "bullseye-backports" and
"buster-backports-sloppy".
That should be fixed now. We changed the behavior of the repository so
files can be shared between uploads as long as they have the same
content (checksum).
You can upload two version sharing the same orig and it will work fine.
Note that, shared files have the same restriction as other files. If the
content changes, all uploads using the previous version of that file
will be removed from the repository to keep consistency. The dsc link
for removed repository files should not appear in the package page.