I'm not sure it does. For most of the post-war period, the German left was openly contemptuous of German nationalism and consequently the idea of "national unity" implicit in Kaiserguard's explanation, advocating instead a civic or constitutional patriotism which assumed a break with the traditions of the pre-1945 era. (You'll note that, even today, German anti-extremist legislation is framed in terms of the "Defence of the Constitution".) At the same time, the German right consistently attempted to de-nationalise the Third Reich, framing it as an aberrant episode with no deep-seated or peculiarly German causes, but a product of short-term, pan-European upheavals, and deeply resented the idea that German nationality needed to be in any way redeemed or justified. Meanwhile, East Germany cultivated an idiosyncratic German nationalism based around a counter history of leftist or perceived leftist figures from Thalmann down to Müntzer, and explicitly anti-"unity" insofar as unity meant unity with "bourgeois" forces which they regarded as responsible for the Third Reich in the first place.
The explanation Kaiserguard gives, that Germans both view the Third Reich as a national phenomenon and that the nation is something worth preserving, is really an attitude of the post-unification period, a product of Germans' attempts to rediscover a sense of co-nationality with people who'd spent the last forty-five years on the other side of a military boundary, and while it certainly describes some German's experience of their national identity, particularly (I understand) of younger people living in the former West Germany, it's not universally true.