+1
I’d believe it. People who have baked their chiller and carbonized whatever hop or protein deposits are inside find that black water does come out for a while. Is that a problem, though? Probably not, as long as you pasteurize it with some hot wort recirculation. When I used a plate chiller, I didn’t trust just using sanitizer because most of the ones we use as homebrewers are quickly inactivated by organic material.