To the OP, to my knowledge, it has never been disclosed to what degree the perimeter attribute plays into a player’s “pure shooting” ability. Even if you could isolate the attribute among the others that determine whether a shot goes in, you still have offensive set, distribution, and a player’s 3-pt frequency setting to factor. This is basically something left to user interpretation. It’s an interesting question, to which there are many possible answers, but they’re all going to be subjective and speculative.
FWIW, if I’ve got a high per freshman coming in, I will generally set him at 0 or +1 and let him shoot a high percentage of 3s, but keep his overall distribution low until his IQ gets to the C+ range. Players with good IQs can be effective 3 point options even with lower perimeter ratings. Upperclassmen at D1 under 70 per can shoot 40+%, as long as the frequency is not set too high.