Snod, your expectation that Devers will maintain his average walk rate as a 20 year old in his first call up is totally unreasonable. Taking two of your examples - JBJ had an .097 isoD in MiLB that included a .115 isoD in A-A+ in 2012. Lindor had an .075 isoD in MiLB that included a .079 isoD in A+-AA in 2013.
As a 24 year old rookie JBJ's isoD dropped to .067, approximately .030 worse than his career MiLB line. That has risen to .075 this season after almost 1500 MLB plate appearances.
As a 21 year old rookie, Lindor's isoD dropped to .040, or .035 worse than his career MiLB line. That has risen to .060 this season after about 1000 MLB plate appearances, so improved but still not at baseline.
Currently, Devers has accumulated a .058 isoD. Dropping that by .030 makes it a .028 isoD. For reference, Pablo Sandoval had a .047 isoD in his terrible 2015.
I have long thought Devers would, if given sufficient time and opportunity to struggle and develop at the MLB level, become Big Papi's successor in the lineup. However, David Ortiz had a .082 isoD in the minors before his rookie season at age 22.
To this point, Devers' .058 is most comparable to Will Middlebrooks' career MiLB .055 isoD. I'm a believer, but would have liked to see him get more time to mature as a hitter in AAA.