Jeskai Control's spells are split between red and blue. Firebending Lesson, Combustion Technique, Abandon Attachments (hybrid blue/red), Thor, Tablet of Discovery, and the multicolor Jeskai Revelation are all red, so Flashfreeze has plenty of solid targets. Their blue spells, such as Divide by Zero and It'll Quench Ya!, are out of its reach. Negate stops their biggest noncreature swing spells like Jeskai Revelation or Tablet of Discovery. Ashiok, Dream Render exiles their graveyard, which shuts off the Lesson count that Gran-Gran's cost reduction and Combustion Technique rely on, and it leaves Thor's enter trigger with no card to target. Get Out and Winternight Stories are cut since they have very few creature targets worth countering (just Gran-Gran and Thor) and no enchantments, and you need to prioritize protecting your own threats and countering their key noncreature spells instead. Keep Stubborn Denial as premium interaction against their noncreature-heavy deck.