I disagree, while I think riding should still drain the rider's stamina, the horse's own stamina should be a limiting factor. It's even crazier for a horse to run further just because the rider is a big meatwad than it is for boat travel to have no stamina limitation.
I think boats working the way they do is a development compromise. If it drained stamina, or it travelled more slowly, it would just make boat travel more tedious. In the current version of H&H, overland travel is (very unrealistically) almost all straight lines, because the terrain is mostly totally flat and open everywhere. Boats need to be preternaturally fast and easy to use to maintain the right balance between the effectiveness of land vs. water travel.
H&H 2.0 is going to have cliffs, elevation, and other new terrain features, so that imbalance is not going to be there anymore in it; boats won't need to be quite as effective because overland travel will involve more detours and complications that river travel (so far as I know) still isn't going to have, or at least not as often. That means the world won't need to be as big to feel as big, which is another big plus.
I'm looking forward to farms needing to be levelled or (labor-intensively) terraced, too. If you can't plow a big field because the terrain is too hostile, then it's not just about biome and soil quality anymore, and there's something new (and obvious) to consider when selecting a site for founding a new village (or for a new conquest.)
It also changes the gameplay for those who do live in rough terrain to be much more flavourful; a hermit hillman won't just feel like they're running a mini-village on their own, but it will actually feel like they live in a trackless wilderness that they might know like the back of their hand, but where the average player wouldn't dare tread. There's some of this effect now (woo, thickets!), but the new terrain will enhance it a great deal, I think.