I don't doubt the Sox reasoning with the decision not to call up Devers "before he is ready".
I'm not sure I'd say it would be "disastrous" to do so. I might not even say it "probably" would be disastrous, but I have no issues with Sox management in this area. They have a pretty good track record at knowing when the right time is.
Weighing an extreme team need vs the possible pitfalls of calling a player up "before it is time" is one tough decision to make.
Not all pre-MLB games and PAs are equal, and it's not as easy as just looking at professional/college experience and age to determine ML readiness, but here are some numbers:
Beni: 126 gms & 551 ABs in college/151 games & 657 PAs in the minors.
TOTAL: 277 games and about 1280 PAs before call-up at age 22.
Moncada:101 gsm & 367 PAs in Cuba/256 gms & 1172 PAs in the minors.
TOTAL: 357 gms and about 1540 PAs before call up at age 21.
Due to Moncada's MLB struggles, many feel he was "rushed" more than Beni, perhaps because of Beni's relative ML success. Many felt both were "rushed" out of "desperation".
Betts: (no college)/299 gms & 1315 PAs in the minors before call up at age 21.
Most felt he was not rushed, but he did not have much time to learn the OF before being placed there FT.
Bogey:(no college)/378 gms & 1623 PAs in the minors before call up at age 20.
Most felt he was rushed, and he only played 3B for 10 gms before being called up to play 3B in the heat of a championship run.
Devers: (no college)/385 gms & 1506 PAs in the minors + 38 gms & 125 PAs with Escogido.
TOTAL: 413 gms and 1623 PAs. He is 20 now.
As you can see, only Bogey had more games and PAs than Devers before being called up. Like I said, all games and PAs are not equal. Not all players are "mature" at the same ages either, but Devers has had a lot of time playing professional ball. He started at age 17 not 18 like others. He got way more PAs at age 17 and 18 than Beni did in college at ages 18 to 19. He's had 2 straight seasons with 500+ PAs and has over 300 so far this year.
Again, I'm not saying I know better. I trust Sox management on knowing the right time to call Devers up. Lin and Marrero are "buying more time" for Devers, and that's great, but at some point, team need or desperation may trump readiness assessments or Devers will be deemed ML ready on his own. His time and experience in the minors seems equal or more than most of the recent Sox players promoted to the bigs. although much of it was at low levels in the system, but over 400 games and 1600 PAs is quite a lot.