Another thing to note, the shadow does respawn, but it respawns weaker. It's the only different shadow, not a lesser one like the rest. After the first respawn, all are the same.
And there should be two respawning, shadow1 and lshadow1.
Like I said before, I think the case for leaving it be is stronger than for enabling. Besides what was already said, just looking at the ini gives me an impression that the timeline was like this: all spawns are shadow*, then they disabled them by gimping the spawn groups, then they added shadow1.