"When there are only two players remaining in a poker tournament - the small blind is the button and acts first before the flop and last after the flop. The player who does not have the button is dealt the first playing card."
http://www.homepokertourney.com/button.htmRRoP is the closest thing to a de facto standard as there is. Button is SB in any tourney worth its salts. As for websites that claim otherwise, a) this is the Internet, you can *always* find someone to say something contrary to the facts b) let's hear what sites they are.
Their confusion may well have come from not knowing how to set the button properly after a player busts out in third place (see same page as above) but that still doesn't make it right.