I'm in the middle of assembling a 400 block stroker motor with aluminum main caps and ARP main studs, the instruction do say to "hand tighten" (not finger tight ) the studs only. I've had the main caps off and on several times so far checking clearances, each time I remove the studs to walk the caps out of the block, each time one or more of the studs has backed out a little when removing the nuts, some of the studs also act like they move into the block a 1/8 to 1/4 turn more when torqueing the nut down
I do use the proper size allen wrench to "snug" the studs a tiny bit into the block
OP, I have had one rocker shaft break on the dyno, that stud was loose but what I found out later was that I was using to much torque on the hold own studs or bolts
Once I started using the factory torque specs(23 to 25 ft. Lbs.) on any of the BB rocker shaft fasteners I used that problem stopped