I really think someone on their team saw a promotional material item and it was believable enough to post it to their website. They might have heard a snippet, but the fact that they didn't allude to this being a part of the 50 Shades soundtrack (which at this point is the only thing that makes sense b/c I can't hear Nicki on a remix to Pretty Hurts) makes me think that they either didn't put the puzzle pieces together or they didn't want to give it away.
Imagine if she is on the remix to Crazy in Love even though it seems to be a duet between BOOTS and Bey.