A case for the German administrators of the site:
The "Ostereistedt Steingrab" is a passage grave and not a chambered tomb. The relevant literature from the offical responsible archologist Dr. Tempel describes the large stone grave as a passage grave.
You can check this information here:
Tempel, Wolf-Dieter (1999): Auf ur- und frühgeschichtlichen Spuren durch den Landkreis Rotenburg, Wegweiser zur Vor- und Frühgeschichte Niedersachsen - Heft 22, Oldenburg p. 33-34
Or on the Wikipedia page:
https://de.wikipedia.org/wiki/Ganggrab_bei_Ostereistedt
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