The default BLUFOR loadouts have grenadiers with 3GL (which is a Metalstorm 3-round launcher) with only normal 1-round grenades.

The 3-round Metalstorm type grenades are currently only attainable by scripting, AFAIK.

Shouldn't the 3-rounder be the default one for all BLUFOR grenadiers already in 2035, or is it a "balancing" decision? Or a story decision (I don't think the 3-rounders are the super secret NATO weapon from the old storyline, right)? Or simply overlooked?

Because of this, even many user created missions are missing on the "cool" 3GL 3-rounders because people almost always forget they exist, and would have to either script globaly or add them in the init field of every grenadier in the editor.