Ruby Storm needs to chain many rituals and cantrips in a single turn to go off, so High Noon's one-spell-per-turn restriction is close to a hard lock on their kill turn. Force of Negation is free interaction on their turn to strip Ral, Monsoon Mage or a key ritual before they can build toward Grapeshot or Past in Flames, and since they're mono-red you can hold it up without fear of losing tempo. Isochron Scepter is too slow to interact with a combo deck that can kill out of nowhere, so it's the cut in favor of proactive disruption.