If you acknowledge that doing it may cause a riot, how does that not fit into a loose definition of “inciting a riot”? I’m trying to think of a more innocent act that might start a riot that would obviously not be “inciting a riot”, and I’m struggling to come up with a counterexample.

It’s not ideal, but I’d say the reason they require equivalent pricing is, so that people don’t just use Steam as a marketing platform, while diverting all sales to their personal website where they sell the game for $X cheaper.