What a lame response. It has everything to do with the WC's claim that YOU support. Why can't you show that CE 573 is relevant as claimed?
This is a classic example of shifting the burden that LNers employ constantly to cover for the fact that they have NO supporting evidence for the WC's claims they support wholeheartedly.
You are the guy who claimed that there is "NO [you like to capitalize that for some reason] chain of possession for CE573." Not just, "the chain of possession is weak" or "the chain of possession is muddled" or "the chain of possession has gaps" or anything but, "there is NO chain of possession." Again, that's a very specific, direct, and unambiguous assertion.
It's your assertion, so it's up to you to present a supporting case for it. It's pretty funny that you constantly try to shift the burden onto others, and when they point out that you're responsible for your assertions, you complain that the are trying to shift the burden on you. Well, that's where the burden should lie in this case. You.