I don't know if this is old news, but it is certainly strange...
It would seem that being SMN main job boosts Wide Scan I to Wide Scan II for no apparent reason. As THF75/BST15, the Wide Scan was approximately 1/2 a map square (pretty much sight range), but as SMN75/BST15, it was ~2 full map squares (in the same zone).
I didn't test this with any other job combinations yet, and I didn't test with /RNG to check if it granted +1 to Wide Scan or if it just put it to Level 2.
(For those that don't know, BST has Wide Scan I from 1-20 whereas RNG starts with Wide Scan II at lvl 1)