Does map completion provide any benefit?

Is there any benefit to getting map completion in this mini league? If we don't get atlas points, then what do we get for completing maps? Wondering if I should even bother trying to fill out my atlas.

Also, orbs of unmaking are still dropping. Just carry these over at the end of the league migration, I guess.

Yes, some of the idol slots require you to have a certain amount of maps completed. This includes one slot requiring 115 completed maps, meaning all of them.