Being poly does not mean one has to accept any and all sexual connections wanted by a partner. Not does it mean that feelings are not felt. SC was uncomfortable because of the specific circumstances of her husband's possible sexual connection with a dear friend - a friend going through a bad divorce, fleeing an abusive partner. I would have very similar concerns in her shoes. That has diddly squat to do with being poly. Also she has acknowledged that her husband is more poly sexual than polyamorous.
You don't have to accept SC's version of poly for yourself. But it is still poly.