I have no angle here (or "I have no alpaca in this race", as they say on this board.)

I'm just observing and it is quite obvious that "I offered a letter of credit" and "Companies do not spin up $20M worth of product on letters of credit" are not even nearly synonymous and you somehow suddenly switched sides between yourself and Xilinx. This is a very definition of a word "shifty" as it is used in business negotiation. It is quite obvious that you hiding something material and they must have found this while negotiating the terms. If you habitually talk in a business meetings like you post here on this forum then I completely don't wonder why they get suspicious, require prepay for everything and count their fingers after shaking hand with you.