Yeah, I don't generally venture into Nintendo topics so maybe that's why, but I've heard neither of the points raised in the OP about those two games. Whoever seriously speculated that Mario Odyssey would be an endless runner was a fucking moron.
It was a day before the January presentation IIRC, someone just came out of nowhere and brought that up as "wouldn't it just be Nintendo being Nintendo if this was a 3D endless runner" and yes it was incredibly stupid and off base.
The tech demo thing was *far* more widespread. People comparing it to the so-obvious-it-doesn't-need-explaining tech demo Zelda trailer shown for the Wii U, going so far as to accuse Nintendo of lying (seriously that's become so common over the last year) for showing a seemingly transparent vaperware 'game' on the unveiling of their new system. It was kinda nuts for a bit, you were seen as the silly one if you believed that was representative of a real game, people going so far as to say what we saw in the trailer would never be seen again and they were 100% certain of that fact.
That would be my pick, just before the game's launch with it looking amazing and all.