Comment 11 for bug 80902

@Robert
That sounds like a defect; bugs can have multiple ubuntu /
ubuntu-source-package tasks, so retargeting a task when there is an
existing source package/distro task seems fine per our model.

I think you misunderstand. Yes Ubuntu can have multiple bugs represented
as task for many source packages. A source package cannot be listed twice
in the affects table...that would be duplicate. Nor can you add a new task
for a source package if only Ubuntu is affected. You can retarget the distro
task to the source package. An alternate workflow would be to delete the
distrotask and replace it with a source package task.

The general principle is refine the bug to a specific package or set of packages.
Generic targets like a distro do not provide the information needs to make a
fix.