Well, the S100's payload isn't exactly phenomenal - 50 kg maximum, 25 kg if you want to have some sensible range (about 200 km mission range then, which is roughly matched to that of a Lynx without drop tanks).
25 kg probably wouldn't fit some integrated sensor package they'd want on it. And the hangars on the K130 definitely fit something bigger than two S100 after all.
BwPlan 2009 provides funding for a MALE VTOL UAV (within SAATEG procurement, which also includes the Predator or Heron TP question for the airforce). The Camcopter S100 definitely doesn't fit the category though.
The trials on a K130 should mostly be seen within the BWB's (not the Bundeswehr's) tendency to test out whatever is on the market, and its penchant for supporting the German defence industry in export-related matters. While Camcopter is well-established in sales by now for land-based applications, the BWB was facilitating a sale for ship-based applications as well.
While gaining substantial data on a commercial product that might interest both the Bundeswehr for mission-related procurement and perhaps several German police forces, including the "Coastguard".