In fact it makes it seem the fault of the prosecutor even and not the court. Quotes from the prosecutor from the Telegraph article.
> "It has led to consequences I was not able to foresee at the time."
> "I think we should probably invest in an internal education in the [prosecution] authority, as cryptocurrency will be a factor we'll be dealing with to a much greater extent than we are today. The more we increase the level of knowledge within the organization, the fewer mistakes we will make."
I'm not familiar with the swedish legal system (and not a lawyer), but often you can only be convicted for things the prosecution requests/accuses you of. Otherwise you can't defend yourself in court.
So the prosecution ordered the bitcoin to be seized as proceeds of the crime, but not in a correct way, so the court ruling contained the same wording that a specific value in swedish Kronen shall be seized. Had the prosecution demanded the seizure in terms of Bitcoin instead, the court would probably have approved it too. However, at this point it's too late to change the ruling. Courts exist to settle things, and one can't simply re-roll a prosecution case unless there were grave mistakes.