KA beats Minato, impossible to argue or debate with, lack of feats doesn't imply a lack of power. Character's given a reputation within the manga and novels removes the need for feats.
It's not speculation. Kamui's speed was greatly decreased due to Obito having one eye, and teleporting things through one eye caused a bit of straining for him. The speed of Madara's truthseeker balls were impossible for Obito to dodge with only one Kamui, but when both eyes were used to teleport him, his speed was insanely increased. Had he used both eyes on Minato, he'd have been soloed.
KA defeats Minato. Tsukuyomi can only be broken by an Uchiha with their Sharingan, Minato doesn't fit the bill and Tsukuyomi has killed people in the novels, meaning Minato is a goner, and Obito with no knowledge nerfs would possibly kill Minato.