Interestingly, Kenpom argues (back in an old blog post) that a team's defensive prowess on 3 pointers SHOULD be assessed based on a team's ability to prevent the taking of 3s rather than % made.
https://kenpom.com/blog/3point-defen...-opponents-3p/
With few exceptions, the best measure of three-point defense is a team’s ability to keep the opponents from taking 3’s...When someone discusses three-point defense in terms of three-point percentage, they might as well make the leap to discuss free-throw defense in similar terms. Teams have much more control over how many three’s their opponents shoot than how many they make.