Belcher is a pure combo deck aiming to cast Goblin Charbelcher or assemble Lotus Bloom-fueled mana explosions, so Force of Negation lets us counter their key noncreature spell for free on their turn. Consign to Memory is premium against colorless spells like Goblin Charbelcher itself and Lotus Bloom, and can replicate to stop multiple pieces of their combo turn, while also hitting triggered abilities from things like Hydroelectric Specimen. Erayo is far too slow and Key to the Side-Door does nothing proactive against a deck that can kill from nowhere, so both are cut entirely for maximum counterspell density.