In my opinion, the biggest argument for moving the worker to the mountain was cracker's desire that we look around first, which led him to create a bonus for those who did. I have no idea how dedicated ainwood is to this concept. I hope it is somewhat less than cracker, as most generic starts don't offer the sort of opportunities that cracker gave us if we looked around. I had come to feel that the best reason to look around in GOTMs wasn't because it was always the best general strategy, but the best strategy given the game designer's predilections.
In this case, the river is on the visible side of the mountain. It's hard to imagine what could be on the dark side of the mountain that would make me move in that direction, given that I would probably lose the river's advantage. In all likleihood, anything really attractive would be a few tiles away. If so, I don't think there's much of a loss by building on the spot, putting the worker to work right away, and founding the second city over there. And of course, if there's nothing so great there, then it's much better to settle on the spot.
I think the delayed-contact rules changes adapted from C3C are terrific, and hope we keep them in subsequent games. It keeps the game interesting for much longer - not just in terms of learning the map and plotting mega-strategy, but also in terms of researching, since widespread early contact is no longer guaranteed. That said, I agree with zagnut that our neighbors aren't likely to be as far off as thy were in GOTM27. For me, one of the points of the new rules isn't so much that you have to wait until navigation to meet everyone, but that you have to earn your contacts if you don't.
Given the reduced early contact, one of the gambles we must make is whether to first research pottery, or hope to acquire it by trade. The space-race key will give us some odds, but you can't count on odds. In GOTM27, our mediocre starting spot made the building of granaries a toss-up, as the results showed. That may be the case here. Once I found my capital, if I don't see any compelling reason to build a granary, I'll research writing; if wheat or cattle become visible, then it's pottery.