Yeah, it is one quirk that is odd, I admit... and you're right, it's primarily for system balance reasons that it is that way.
Oh, a point a forgot that I had in my mind while typing the above: most of our small races get a natural racial boost to Dexterity, either as their major or their minor - this is how the system represents the benefits of their smaller size now. (And incidentally, one of the many minor yet pervasive minor factors that make Tasha's lineage system removing racial ability score bonuses actually a very BAD move from wizards, and not one I supported)
