So legacy maps will be useless for targeted atlas players?

From what I understand, using a legacy map will complete the same map in the atlas and unlock every map leading to it. This is great for people wanting 100% unlocks but for people wanting to control their map pool it makes them basically obsolete past a certain tier.

Did I get my facts right?

It's still a head start and you can disable the unlocked map later if you don't want it at that tier.