I tend to agree with you. It is strange in the sense that the government is free to build such software itself, and subpoena Apple for such knowledge to do so, but instead is compelling Apple to act in a substantial way. For Scalia's reductio ad absurdum, could the govt use All Writs to force a safe maker out on the battlefield in Afghanistan to open a safe? If Apple had a working quantum computer, could they be compelled to use it to aid the govt? What's the limit on All Writs if this instance were upheld?