Since #TSA at SFO wanted proof of airplane approval (I asked for it, but at least Lufthansa doesn’t have a workflow) and called a Homeland Security Explosive Specialist for further inspection:
Does anyone know how to best carry larger 101-160Wh batteries on airplanes?
I placed a printout of https://www.faa.gov/hazmat/packsafe/resources/airline-passengers-batteries under the battery.
End result was disassembling the 12Ah hard-case into 2x6Ah (less protected) batteries that are below the 100Wh threshold.