Thanks for "Pomaks". I hope that PMK1 will agree that this alternative name is a fact. As for your example with Lipka Tatars, it's interesting and let see how it is applicable in our case:
As I see, the only argue was about the title of the article - Lithuanian Tatars or Lipka Tatars. In fact, in the artice is clearly explained that "The name Lipka is derived from the old Crimean Tatar name of Lithuania." It was chosen the name by Tatar origin ("Lipka") as a title, but the alternative name is mentioned in the text. I didn't noticed some argues or evidences that there are alternative names as "Russian Tatars", "Ukrainian Tatars", "Latvian Tatars". Concerning "Polish Tatars", it is mentioned in the text "Polish Tatars" (and "Polish-Lithuanian Tatars"). It would be interesting to look about some sources about hypothetical existing of such alternative names ("Russian Tatars", "Ukrainian Tatars", "Latvian Tatars") in the past or in the present. I am sure that if they exist, we can add this useful information in the article. It would be very good test for our case, too. However, until then the good example with this group is hypothetical.