You can only cast a sorcery during your main phase when nothing else is happening
Almost all the red decks in Pioneer would love a way to utilize their mana on awkward turns, and Phoenix of Ash fills that role perfectly
Now imagine how much carnage would occur if you cast an Arcbond or Blasphemous Act in such a situation Its not a totally new idea to combine redirection and damage doubling in this way, but having such a key effect in the command zone is a very sweet bonus
Like most Magic: The Gathering cards, the value of Yuna's Whistle depends on a few consistent factors: its rarity, the printing and finish (regular or foil), its physical condition, and the set it was printed in (Final Fantasy Commander)
As if this wasnt enough reason to be excited about Stolen Uniform, its also great in Pioneer
The first expansion, Arabian Nights , followed a few months later with 78 more cards