Sebep: After an objection I've re-evaluated this and find that the run does not provide explicit proof that all ducats were taken from East Frisia. 25 warscore takes 5 loans worth of ducats which East Frisia technically could have gotten through gifts or some other way. I think it's likely that you did get the achievement so if you still have the save file (and didn't play any further) please send it to me or another mod on Discord, and we'll use it as supporting proof to re-verify the run.