the only thing bothers me, why they still consider the tame cats as ferals.
They DON'T, but if your voucher is for a feral, then that is all they know! Even when there is a TNR group of cats going in for their surgeries, they do not always know which cats will wake up and be "tamable". That is why some cats who are placed for adoption have had their ear tip removed. (when the cat is under anesthesia, who could tell the wild from the tamable?).

So if you used the vouchers for ferals even though they are tame pets, than you got what you paid for (so to speak).