Ammo designed to perform admirably in longer 9mm barrels may not be optimal in short 3" barrels. One tester did a study of .380 ammo and it showed the favorites shot from 3" barrels were middle of the road. There were better loads that few were aware of or would use that out performed the most recommended.
I'll go out on a limb and say 9mm is no different. The issue is that one inch of barrel length is a 25% difference in dwell time with the bullet absorbing energy. From that perspective it could be said it's significant. And that is what showed up in the .380 testing - expansion and penetration fell out of the front running or exceeded a known performance standard. LIke the FBI protocol.
Your choice to accept their standard, but the idea is to get the bullet to lose most of it's energy in the target and not just go whistling thru because it didn't have the velocity to expand fully. Hardness of the projectile material and the structure of the tip seem to control that, and it can vary enough that out of shorter barrels they don't do as well.
I choose the bullet first - Hornady XTP's seem to perform well across the board - then what load appears to have all around performance. Not necessarily the most expansion or the most penetration. Frankly when shooting a live target, there are so many variables that it's not going to be exactly what a range test would indicate anyway. And for all the superior gel block results possible, if it won't feed reliably and has extraction issues - it's not a good choice. Far too many pick the one with the biggest numbers when in real life it really doesn't require that. Just consistent performance. What can be far more important is shot placement.
Nobody likes to choose an "adequate" round and places too much confidence on the Bullet of the Month - because they think they can't miss and will get a one shot stop. Better to competently place adequate bullets in the right spot consistently than be forced to shoot more and more "superior" bullets because shot placement was inadequate.
More practice with shot placement is a better answer than more expensive bullets and not practicing. It's hard to see thru the marketing hype but a better bullet can't make you a better shooter.