Users can’t see what’s in the other region until they get there.
The scenery system’s connection to the core simulation is actually pretty new; it doesn’t affect things as much as it ought to, yet. Definitely adding more scenery items won’t currently make a big difference to people’s ‘scenery’ needs. Right now, it’s mostly just Landmark objects that affect that.
(Although I believe that scenery objects specifically around landmark objects make a difference, via their contribution to the landmark object’s “Beauty” rating. I’d have to double-check that to be sure, but I think that has a small effect already.)
Edit: Technical points; in the current build, players think that visiting a new region they’ve never seen before will give them 30 points of scenery. They think that visiting a landmark will give them 40 points of scenery. So as long as the landmark is closer than the other region, they ought to generally prefer to visit the landmark, rather than the other region. Note that the decision between the two destinations is performed before pathfinding; it’s only considering straight-line distance, to determine the estimated travel time to each destination. If that’s not working, it’s likely a bug, and I’d be interested to investigate!