Reportedly some teams have exit physicals when the season is done. I would imagine part of the reason is to see if anyone does need surgery in the off-season. No idea if the Sox do them or not. Or if this would have been caught in one. (Reportedly Story was warming up for the WBC when he noticed the issue.)
I’ve never played 162 game season, but I’m guessing after one, every single MLB player is sore all over. It’s basically a 3 hour game a day for 6 months. And most of them, if not all, probably think “this part of my body was sore last year, too, but a few months off and it will be good as new again. Just like every year”
And most of the time, they’re probably right. But when they’re not, it can go unchecked until even later than Jan 10.