There's always been a disconnect between people who understand technology and people who write disclaimers and laws. Being smart doesn't protect you from doing something which is a violation of the law, even though there may be gray areas. Yes, watching the cached video might be a gray area - but the spirit of the disclaimer is obviously to prevent storing it in such a way that you can't access it unless they can provide it at the point of request.
https://xkcd.com/1494/