Alright, so here's the gist with this one.
I just pushed the change to Disco, and I got clarification from Adam that the change needs to be SRUed to Cosmic as well. Brian Murray asked me to wait until the current change queued has been ushered into cosmic-updates and we can proceed with SRUing from there.
I'll check back when we're at that point. In the meantime, Cosmic -> Disco upgrades should be checked with a dummy lubuntu-core package to make sure.