IMHO, the phrase "Bug reports and problems specific to development version of Ubuntu should be reported on Launchpad so that developers can see, track and fix these issues." is an excellent reason and doesn't need to be clarified or restated in any way. It not only indicates where bug reports should go, but also why. While there are many confusing things in life, I don't believe this is one of them.
Edit:
As I believe we comment as to which bug we are referring to on current releases prior to voting to close as a bug, I don't perceive a problem here. If someone has a problem with a current version, if we read and comprehend the question I don't see how it gets tagged and closed innapropriately (even if newer versions are mentioned in passing) "Due to this I'm considering an upgrade to 16.04" doesn't indicate (at least to me) that the user is running that newer version.