The adjustment nobody films
Almost every incoming professional arrives with the skills that made them worth signing. What they lack is calibration: how fast a rotation closes, how much contact is allowed, how quickly a window shuts. That recalibration is invisible on a stat sheet and takes most of a year. Judging it by season averages is like judging a translation by its word count.
Unstable roles, unstable numbers
First-year minutes tend to move around, sometimes weekly. Numbers built on shifting usage cannot be compared to numbers built on a stable role, yet they routinely are, usually to declare someone a success or a disappointment before either is knowable.
A better question
Instead of asking what a rookie averaged, ask what they can do in month eight that they could not do in month one. Are they arriving earlier on defensive rotations? Are they making the second pass? Those changes predict the following year far better than any total, and they are visible to anyone watching with the right question in mind.