So KNC would not accept even Bitcoins as a security in order to send working boards first as to minimize downtime for customers.
From where I am standing it looks like they are trying hard to work against their customers by refusing to come up with a RMA solution that works for both sides.
I can not think of a single reason why they would not accept BTC as a security in order to send working boards first, apart from trying to discourage people from using the RMA service.