I have to say something here. We agree that, as written, this is how the spell works. Push is from the mage as origin, because Tsunami does not specify otherwise. Also it doesn't affect walls at all. We can come up with fluff of our own that explains this weird behaviour, and usually I am the first to defend MW when the cards are ambiguous.
But really, I think this is one of those cases where it's ok for AW to come out and say: "Sorry, that was a blunder, we didn't consider that. Here is how it should work."
Am I the only one thinking this?
Of course, I might be wrong, maybe it is as intended, but I have my doubts about it.