Historically caffeine in all forms was frowned upon in Mormonism. Only in the last 20ish years has that started to shift. There are some Mormons who still take the no coffee/tea rule to its logical end and avoid caffeine altogether, but most have no qualms ingesting it in holier forms than drinks served at the devil's temperature.
That said, who knows where Mantz and Young stand on it. Mantz doesn't run Sundays, which puts him a little more to the extreme side of Mormonism. He may also be on the extreme side regarding caffeine.
Speaking personally, I did not take caffeine for racing/workouts for a long time because I was one of those uber Mormons for a long time. Not until my late-20s. It would not surprise me in the least to find out Eyestone's guys are in the same boat.