The “long sword” in D&D is misnamed. What it should properly be called is an arming sword, or broad sword. Historical longswords were designed for 2-handed use, and are nearly synonymous with greatswords.
Splint mail shouldn’t even exist in a world with full plate. It’s the equivalent of muskets alongside AR-15s.
Why is it so? Remember the freedom of 1e that I praise? Well, sometimes it works against itself. In the 1e PH there’s several pages of equipment listings, costs, and statistics. What was supposed to represent what might be available in a game setting was taken as what should always be available. This is why there is no accounting for obsolete weapon and armor forms. Sure, someone ignorant of the evolution of armaments wouldn’t notice, and there’s always the fallback of “it’s just a game, don’t care so much”. But to me, it stands out like someone with so little knowledge of baseball, that he keeps the glove on while at bat.
Fortunately, BG is already very limited in its animations, so pruning the excess of items won’t be a problem visually.