Confused by LCM filter effect with Ubuntu 20.04 channels

[ppanon2022]

We've been using the LCM facility to stage consistent package sets through sandbox, staging, and production systems. We've got a base filter for denying packages more recent than a cutoff Patch(Issue date) value, which we change and reuse each patching cycle. Now it turns out that we're using the Percona Xtrabackup (for MySQL online backups) via a custom child channel. Percona requires that its version be the same as MySQL, and MySQL made our patching cutoff date but Percona's matching release was a couple of weeks later and missed the cutoff date. I've therefore tried to add a new filter - using the package (Name) and allowing just the percona-xtrabackup packages - to the LCM project and rebuilt that project.

The weird thing is that now a whole bunch of new packages show up as being needed for the test systems, including kernel packages that appear to have been synced recently and therefore long past the deny cutoff date. I did not change the cutoff date prior to rebuilding the project so it doesn't seem like there should be any of these new packages. Any idea why that would be happening?