While this is true to some extent, I think the question is mostly one of mutual intelligibility; that is, whether a speaker of dialect A and dialect B can under

While this is true to some extent, I think the question is mostly one of mutual intelligibility; that is, whether a speaker of dialect A and dialect B can understand each other by each speaking their own dialect. This is obviously a spectrum - there can be no mutual intelligibility at all, some amount of mutual intelligibility (like among some of the romance languages), near full mutual intelligibility, and full mutual intelligibility. So, where the line is drawn depends upon political factors. Despite all of the PRC's claims to the contrary, Chinese is not a single language but a language family. There isn't really much you can do politically when mutual intelligibility is low.