The reason is because the UW one feels like the default commander and White makes Allies the best for waterbending purposes, but Black offers some really powerful waterbending spells and more Clues for waterbending purposes
People may try to make a combo deck work with Animation Module and Metallic Mimic as well, but overall, I think Srams Expertise may see more play than deserved in this upcoming combo-heavy format
On the 2nd day we ship your decal
A sorcery for three mana, Zoological Study allows its controller to mill five cards, returning a creature milled this way to its owner's hand
Field Surgeon Gateway Shade Gaze of Justice Glare of Subdual Grand Architect Grappling Kraken Grove of the Guardian Hair-Strung Koto Hecatomb Heirloom Epic Holdout Settlement Hollow Warrior Honeymoon Hearse Hundred-Talon Strike Hylda of the Icy Crown Impelled Giant Jaspera Sentinel Karplusan Giant Keldon Battlewagon Koskun Falls Kyren Negotiations Lashknife Leyline Dowser Llanowar Behemoth Loam Dryad Lodestone Myr Maro Avatar Master Apothecary Moonsnare Prototype Mothdust Changeling Munda's Vanguard New Blood Nihiloor Opposition Orim's Cure Otharri, Suns' Glory Prismatic Strands Protocol Knight Purple Pentapus Ramosian Rally Redcap Raiders Relic of Legends Revelsong Horn Sage of the Maze Saheeli, Filigree Master Sanctuary Lockdown Saruli Caretaker Scene of the Crime
Unfortunately though, Galadriel, Gift Giver's ETB ability is rather lackluster