When a bug watch has been added in Launchpad, it means someone has triaged the distribution bug report and either (a) linked it to an existing bug in the upstream or (b) filed a bug upstream and linked to that. When this is working correctly, the upstream developer wouldn't be required to look directly at Launchpad (but could if they wanted to).
This is basically the same way Debian maintainers interact with upstream, but with a bit more automation of communication with upstream bug trackers (and more automation planned for the future).
The report gives a good indication of how well that process is going.