He was asked if Joel could be a new type of Rithmatist.
Brandon Sanderson (paraphrased)
He said that it was possible. But when he saw that I put that in my notes, he said "no, he's not. I just didn't want to say it outright. Joel is not a new kind of rithmatist". He may have denied that Joel could be a Rithmatist at all, but I don't remember the exact wording, so I cannot confirm.