Fast tracking vs not fast tracking is really about each individual player and the org plan. That is why looking at the numbers on the farm is such a dicey proposition. The job at the minor league level is not to win - a pitcher could have a 4.50 ERA because he is being told to throw his 3rd best pitch a lot. Benintendi was the Golden Spikes winner playing in the toughest college league in the country - the Sox started him in Lowell and Greenville, and he crushed them, but that was also inferior competition to what he had been facing at Arkansas. He had inferior superficial numbers to Moncada this season on the farm, but clearly was much better equipped to succeed with the big club. He showed the evaluators stuff that they needed to see from him
Devers is so young - he had a good season in Salem, making a lot of contact. Has he done enough to start at AA? Possibly - but it is really about whether he fulfilled the org goals. Devers was among the youngest regulars in High A and if he is in AA he will be the youngest regular there too.
I tend to believe the old adage - players make these decisions for the org largely.