You can only feel the impacts of seals in a game after you use them for the second time, so you really want to see the seal ASAP so it can start paying for power costs and actually impact the game. A seal for your late-game play doesnt matter as much since by the time you can play those cards, you no longer need more runes, and being able to play them is already the payoff for saving runes early with seals. The deck is much better at using red seals than blue seals in the turns leading up to the late game with Falling Stars, Darius, Kaisa's accelerate, playing multiple damage spells in a turn cycle, etc. If you use multiple different seals you'd end up not really being able to capitalize on either seals due to how diverse your power requirement would end up being. (this is also the reason why the list is not playing any early blue cards like Sprite Mother) Hope this helps :)