I wouldn't put too much stock in anything shown on the carving in the announcement trailer myself, after all, it's an artistic carving depicting the artist's vision of what the events foretold in the prophecy might look like, we're not meant to take it literally, and certainly, it may not, and in fact likely does not, accurately reflect real gameplay, and just because we see something on the wall doesn't mean things will look exactly the same in game.
Or if that doesn't satisfy you, remember that Todd has said that they are not sure yet if horses will be in or not, and we will only have them if they can do them well, they would not say this if it was already decided from the start that they would be in, so logically, Bethesda would have known at the time that they created the trailer that it might not be in the game, yet if it still is in the trailer, than that must mean we're not intended to take that literally. Now, that's not to say we won't see it, but it does mean that we shouldn't take the announcement trailer a evidence for it.
Myself, I think there's a pretty good chance that we'll be able to ride horses, but I doubt that mounted combat will be an option, because not only do we need a good horse riding system then, we also need the mechanics and animations for fighting while doing so as well.
All he says is that the Oblivion implementation is too basic. He mentions red dead of a good example of horses done very well, but not once does he say they HAVE to be that quality to put them in. He also mentions there are more games with horses now, and I'm sure none of those are as good as RDR either, but they didn't cut them purely for that reason. I see no evidence that Todd has that high level as the basic standard.
That's correct. He doesn't say that they have to be as good as Red Dead Redemption, though the quote DOES indicate that Bethesda won't be satisfied with a half-hearted implementation of horses, it shows that with more games using horses, if Bethesda does horses, they need to do more than they did with them in Oblivion to compete, but that doesn't mean they have to be as good as Red Dead Redemption's horses, after all, Skyrim does some things which that game doesn't do, and yes, horses are an important part of Red Dead Redemption, in Skyrim, they'd probably geta somewhat lesser focus.