I think they do.
Just like poker players stim by rhythmically playing with chips. And baseball players stim in all kinds of interesting ways.
Now, I am in favor of a public-private distinction. Some stimming that's just fine in private doesn't carry too well in public.
And I think the athletes stim for many of the same reasons we do: to relieve tension, to maintain concentration, to deal with sensory issues.
Do a youtube search for "Steph Curry." A classic photo on the cover of one of the first videos is a picture of him chewing on his mouthpiece in a thoughtful way. And this is THE Steph Curry---two-time MVP, and this year the first unanimous MVP in league history. 