The bolded section of this post got me curious, so I skimmed through the stats for some recent top SS prospects to see what they had done at AAA:
Corey Seager hit .278/.332/.451 in 464 PA in the PCL at age 21, a disappointing season for him after tearing up AA. The Dodgers called him up anyway and obviously he's played well in MLB.
Manny Machado never played in AAA. He hit .266/.352/.438 in 459 PA in AA at age 19, before moving up to MLB for good.
Francisco Lindor hit .279/.333/.396 in 442 PA in AAA over parts of 2 seasons (age 20 + 21). He's showed more power in MLB than he ever did in the minors.
Carlos Correa didn't spend much time in the upper minors, but he hit .276/.345/.449 in 113 PA in AAA at age 20 after destroying AA with a 1.185 OPS in 133 PA the same year.
Xander Bogaerts hit .284/.369/.453 in 256 PA in AAA at age 20. Bogaerts was a consistently strong hitter in the minors who struggled for a bit in MLB, but has gradually improved.
Addison Russell essentially skipped AAA (59 PA of .657 OPS), and he hit .302/.355/.529 in 262 PA in AA at age 20.
Trea Turner hit .306/.354/.457 in 576 PA in AAA over parts of 2 seasons (age 22 + 23). Turner has also seen a bit of a power spike in MLB compared to his minor league numbers.
Dansby Swanson skipped AAA, and he hit .261/.342/.402 in 377 PA in AA at age 22.
Some conclusions:
Many of these guys spent little or no time in AAA, before getting called up, and some teams don't appear to care all that much about performance in AAA.
I'm not sure any of these guys are particularly good comps for J.P. Crawford. Lindor might be the closest based on minor league stats, but Crawford's combination of modest ISO, high BB rate, and low K rate isn't terribly common.