The cost reduction applies only to generic mana in the total cost of red spells you cast
Funnily enough, Wizards opted to leave warp out of the Edge of Eternities Commander precons
The deck is designed to offer a high power level, but meanwhile offers a fun and straightforward play style
Gurmag Angler seems incredibly easy to cast as early as Turn 2 for the deck, thanks to Street Wraith, fetchlands, Burning Inquiry, Faithless Looting, and Cathartic Reunion
The same applies to Serum Visions or unfortunate Lantern of Insight players
Personal opinion: Looting isnt worth spending extra mana on in Commander, so the Gateways not really getting there on its own, and the threat of this flipping is enough to attract the attention of your opponents