If Germany and Poland count, I don't see why the following don't count: Russia (Konigsberg), France (Colmar), Belgium (Malmedy), Denmark (Sonderburg), Czech Republic (Hultschin), Lithuania (Memel), and The Netherlands (Wylerberg).
Its probably because the listed places were colonial (world wide) possessions. The regions you listed were areas within the German Empire itself. Konigsberg for example had been part of Prussia for hundreds of years by 1914.
what part of Mauritania or Botswana were German? And if you count small slivers of neighbouring countries then Mozambique should be on the list too and Nigeria and Gabon
But I can clarify the point by removing Germany and Poland and specifying non-European holdings.