I have Outdoorsman at 150%.
I follow this conversation with Mantis in NCR Train Station:
-Hey, You look like the kinbd of guys taht's been around! Have you mapped out this entire are before?
-Sure do! What can you tech me?
(Here Mantis answers: Study this map. I'll only show you once. [You do so. You can now see all areas of the map!])
- Thanks! Thats all for now, goodbye.
But no Explorer Perk and no map revealed