It can happen at any age. A couple of games back my 2017 leads off the 7th and swings at a first pitch curve -- something he never does. Gets a single to right, and all of a sudden he's replaced with a pinch runner, which is really odd because he has probably twice as many SB's as the rest of the team combined. When he gets home I ask him WTF? He says he told coach he was feeling sick and couldn't hit but coach talked him into going to the plate and getting run for if he got on. He says, Dad, I'm so glad that ball didn't get past the right fielder. If I'd have had to run to 2nd I swear I would have shat myself.
Now on the other hand I AM getting old so I don't remember....
Did I tell this one already? A kid on my LL Majors team hits a HR, then when he gets back in the dugout says, Coach, I really gotta go #2 LIKE RIGHT NOW! I say sure, go for it. We go on to have a really big inning and his spot comes up again. Blue's calling for a batter and the kid makes it back to the dugout just before I send a pinch hitter in, and he hits another dinger.