That's a bit of a stretch, isn't it? People Travel to places they have never been to all the time, and it works just fine. And it isn't as if a place ceases to exist just because someone creates a mountain in what used to be a lake. If fact, we never see a Gateway open beneath the ground, and there is no reason to assume the Traveller always knows the precise elevation of their destination, so maybe Travelling somewhere to find an unexpected mountain isn't a problem.

In any case, you can always Travel to somewhere you can see, and even jumping a few miles at each go is a lot better than using a horse, so Travelling would still be useful if your objections are valid.