Ideally, the package maintainer would do it after confirming the bug, or ask the reporter to forward it upstream in case more information or feedback is required. I assume that this was not done due to the Xubuntu team being short-handed.
Nevertheless, opening an upstream report is in most cases the best choice (unless it is a packaging issue or some Ubuntu specific problem).
Ideally, the package maintainer would do it after confirming the bug, or ask the reporter to forward it upstream in case more information or feedback is required. I assume that this was not done due to the Xubuntu team being short-handed.
Nevertheless, opening an upstream report is in most cases the best choice (unless it is a packaging issue or some Ubuntu specific problem).