Except he did play him, and only after that loss did he withdraw from the tournament and refuse to play with him again. The implication is clear to all that Carlsen suspects foul play in that game, I don't see the point in being coy about that now.
One presumes Magnus believed Niemann cheating in an OTB game wasn't possible; now he believes that's not the case and has decided that even OTB games aren't worth the time/effort/risk.
