I think you have read the manual correctly, and Regulation 13D (3) will allow each tenant two rooms, as they both qualify for the shared non-dep to be included in their household. In matter of fact if 50% of their full rent liability – the “cap rent” – plus 15 quid is lower than the two room rate, they would only be eligible for the maximum rent (LHA) of cap+£15.
The case illustrated (at para. 2.27) is specifically where the non dep is “shared” between households. When the non dep “belongs” to one tenant only, or joint tenants have no non-deps the shared room rate comes into play.
