why do you expect ubunto to submit a patch for every bug they report?
RedHat doesn't supply a patch for every bug that they report to the kernel. sometimes they do, but I wouldn't even say that it's the majority of the time.
taking that attitude that you shouldn't submit bug reports unless you also submit patches is a great way to kill off bug reports, by driving your users away.
nothing in the GPL (or any other opensource license) requires you to create patches, let alone require you to create patches based on problems that people you provided the opensource software to ran into.
they require that you release changes that you do make, and it's strongly encouraged that you push those changes upstream, but if a distro is distributing software and there is a bug in the upstream code I don't see any reason why all the different distros should be expected to create a patch before submitting the bug. in fact I see the idea of them doing so as a massive duplication of effort. if the bug is in the upstream package the bug reports should go to the upstream package where the experts there can look at all the reports from all the different distros and fix the problem once instead of having programmers at the distros who are not familiar with the codebase all scrambling to produce a patch to submit upstream
the fact that launchpad is only a one-direction link is probably as much a limitation of the upstream bug managers as it is of launchpad. none of the upstream bug managers have hooks in them to feed data into launchpad, so they would be reduced to screen-scraping websites (and if they are lucky e-mails) to find changes to pull them back into launchpad.
I think the fact that they can do the one-direction links a big step forward from the common situation with other distros. hopefully the various bug management tools can start creating api's so that they can notify each other about updates. this is a good first step.