UW Control wants to land Teferi, Hero of Dominaria and sweep with Supreme Verdict, so extra Thoughtseize helps you strip their key interaction or payoff before they stabilize, and the second copy is crucial since this is a long grind. Fable of the Mirror-Breaker provides resilient card advantage and a steady token/haste-copy engine that outlasts Temporary Lockdown (which only hits mana value 2 or less, so Fable itself is safe) and dodges one-for-one removal better than small creatures. Cut Biotech Specialist since its Lander token does nothing proactive against a control deck, and trim Lively Dirge since recurring small creatures from the graveyard matters less when they can just Supreme Verdict or exile with March of Otherworldly Light.