No, concentration camps were distributed throughout Germany as well. See here:
https://en.wikipedia.org/wiki/List_of_Nazi_concentration_cam... If you are talking about extermination camps however, then you're more correct.
But I hope the author doesn't rest his claim solely on the fact on which side of the border a camp site was built: Borders between Germany and Poland were "fluent" to say the least until the end of WWII. Especially when he combines "Borders" with "ethnic homogeneity". Many Germans lived in inter-war-Poland, as did many Poles in inter-war-Germany. See here: https://en.wikipedia.org/wiki/German_minority_in_Poland#/med...