This is because the rules of Rush Duels are quite different

If you activate this card when Summoning "The Six Samurai - Zanji," you'll have 2 "Six Samurai" monsters on the field, which will let you Special Summon "Great Shogun Shien." Since "Copy Knight" has become a "Six Samurai" monster, you can also use it to protect "Great Shogun Shien." List of Cards Included Great Shogun Shien Effect Elemental HERO Neos Alius Gemini/Effect Super Conductor Tyranno Effect Enishi, Shien's Chancellor Special Summon/Effect The Immortal Bushi Effect Tiki Curse Trap Fire Formation - Gyokkou Spell Harpie Dancer Effect Powerful Rebirth Trap Parallel Twister Spell Cyber Harpie Lady Effect Blindly Loyal Goblin Effect Elemental HERO Dark Neos Fusion/Effect Neo-Spacian Dark Panther Effect Sabersaurus Normal The Six Samurai - Zanji Effect The Six Samurai - Yaichi Effect The Six Samurai - Irou Effect Shien's Footsoldier Effect Shien's Castle of Mist Spell Hand of the Six Samurai Effect Fire King Avatar Barong Effect Hazy Flame Peryton Effect Elemental HERO Neos Knight Fusion/Effect The Six Samurai - Yariza Effect The Six Samurai - Nisashi Effect The Six Samurai - Kamon Effect Legendary Ebon Steed Spell Swiftstrike Armor Trap Hero's Rule 2 Trap Hero Mask Spell Legacy of a HERO Spell Six Strike - Triple Impact Spell Shien's Scheme Trap Copy Knight Trap Three of a Kind Trap Hazy Flame Cerbereus Effect Hazy Glory Trap Hazy Flame Mantikor Effect Temple of the Mind's Eye Spell

cards becomes much easier when you have the right accessories to hand
For example, lets say you have Jhoira, Weatherlight Captain in play and cast Karn, Legacy Reforged
Destroy this card during your 3rd End Phase after activation
I dreamed that Pocket could be the game for neurotic collectors like me who believe that if you cant collect everything, theres no point in collecting anything