I have all the above be accurate. I even went to the Seattle Sky Club a couple of weeks ago and had two friends. I said I wanted to use some of my companion Sky Club passes and she
scanned my boarding pass and took the passes out of my account automatically. Took about 20 seconds. I do remember a thread from maybe a month or longer about someone mentioning that
they asked to see his Amex card and he couldn't produce it, so they refused entry. Can't remember all the details.