That's going to be a hard question to answer unless Gushue or Howard weigh in personally. I can say as a curler that the curling world is very small. If you want to curl against high-level players often, you need to travel regularly to high-level bonspiels where you meet a lot of the same curlers over and over again. It seems perfectly plausible to me that through curling they'd have gotten to know each other reasonably well.