I too will agree that terrain should have an impact on range. However, there are limits.

In your test map, your platform seems incredibly high. Have you tried to lower it?

What I mean to say is: If I shoot an arrow at you from the top of Mt. Everest, while you're at the bottom, would you get hit? and can you shoot me back?

No, and No.

But If I was on a 100 foot high cliff, then yes, my range should be extended - to a point.

The issue is called "diminishing returns" until such a point it becomes a negative value.

If the archer can shoot 100 feet, and you put them on a 10 foot high wall, how much is the increase? Let's assume 10 feet high gets you 110 feet distance. So at 100 feet high do you expect 200 feet of range? I think not. It would be more like a 10 foot height gives you 110, but a 50 foot height only grants something like 144 and eventually diminishing return nets you negative value, where 90 feet of height actually shoots LESS far than 70 feet height.

So while I will vote to add terrain values to range, the amount of range needs to be calculated