Do they?You mean facial contortions and mental gymnastics don't count?
I mean these kids aren't somehow skilled in the muscular movements required for speech any more than we are. I think a main aspect of what makes up a sport/athlete is that to be an elite contender in that activity you need physical prowess in that activity that the average person does not possess. None of us can jump like AD, run like Adrian Peterson, throw like Peyton Manning, etc., but we all have relatively the same skill in speech production as those kids.
Then, the actual spelling itself, requires a different kind of cognition than other traditional "sport" activities. These kids learn the phonetic rules of as many languages as they can, and then try to tap into that knowledge as best they can when they spell. The strategies they use allow for more concrete ways of winning than I think the cognition for other sports does. Sporting cognition, in my opinion, is motor memory and (depending on the activity; some sports don't require it) specialized kind of learning associated with that sport (Basketball IQ, QBs reading defenses, etc.) that is used to predict the actions of competing competitors.