But taking a step back, there is a much more substantive and important issue with this mantra as a teaching tool for new players
You can always just forego the disguise and cast the card as normal, paying the mana cost and having the creature bravely step out into the world as its true self
To stop the transmute youd need a spell like Voidslime that can counter activated abilities, or a spell like Discontinuity that ends the turn while voiding the stack
Consider Card Interactions: Magic: The Gathering is a game of complex interactions

Orfeo, the Boulder Nimble Larcenist Ob Nixilis, the Adversary Obscura Ascendancy Obscura Charm Obscura Interceptor Ognis, the Dragon's Lash Park Heights Pegasus Queza, Augur of Agonies Raffine, Scheming Seer Rakish Revelers Rigo, Streetwise Mentor Riveteers Ascendancy Riveteers Charm Rocco, Cabaretti Caterer Scheming Fence Security Rhox Shattered Seraph Snooping Newsie Soul of Emancipation Spara's Adjudicators Stimulus Package Syndicate Infiltrator Tainted Indulgence Toluz, Clever Conductor Unleash the Inferno Void Rend Ziatora, the Incinerator Ziatora's Envoy Arc Spitter Brass Knuckles Cement Shoes Chrome Cat Getaway Car Gilded Pinions Halo Scarab Luxior, Giada's Gift Ominous Parcel Paragon of Modernity Quick-Draw Dagger Scuttling Butler Suspicious Bookcase Unlicensed Hearse Botanical Plaza Brokers Hideout Cabaretti Courtyard Jetmir's Garden Maestros Theater Obscura Storefront Racers' Ring Raffine's Tower Riveteers Overlook Skybridge Towers Spara's Headquarters Tramway Station Waterfront District Xander's Lounge Ziatora's Proving Ground
