First of all, a 24 shift attack from a pure mortal (or anything less than a faerie queen, really) is pure bullshit. Yes, I know you found cute ways to justify it, but you still pulled the equivalent of "you lose because I said so and I have all the power".
On the main issue, yes, the player decides if they take a consequence or not. The downside being that when you lose a conflict, you are at the whim of whoever beat you. This is one of the big strengths of the Fate system (the aspect thing overshadows this, which is a shame). Because the player can determine when they take consequences, and whether or not they concede or press the issue, they have the power to determine what is important to their character. They can say "I'd rather lose this fight here, and save my strength for something else" or "no, this matters, I'm pulling out all the stops, regardless of what it costs me in future effectiveness".