Having been in many PT rooms both as patient and observer, I can tell you yes, this is a lot of the times what happens. Doctors and therapists can do diagnostic tests and run scans, but only the athlete knows what they are feeling and when they are feeling 100%.
There's a lot to rip on with the Sox. Not sure Luis Robert being injury prone (or Moncada and Eloy) is really on the training staff. At a certain point it's down to bad luck, the individual's ability to avoid injury, and not selecting injury prone players in the first place. Easier said than done.