Pace - you will recall we have been here before in terms of what Cirrus do and dont recommend.
I dont know the official reason but I suspect that Cirrus will "never" recommend using the chute in "all" circumstances because their lawyers have made clear that would not be a good idea. It wouldnt be a good idea because there isnt (or wasnt) the evidence to prove the chute will most likely result in a better outcome and, even if there is that evidence now, it would still be difficult to counter a legal argument that in a particular situation a conventional FL wouldnt have been better - with the prosecuting lawyers knowing that since the pilot had used the chute (and killed himself) no one could prove what would have happened if he hadnt pulled the chute - you get my drift.
I imagine to ever make the use of the chute a SOP would require a program of testing and certifying that the FAA could never approve and even if they did would be so costly as to make it economically nonviable.
So in the real world we are left developing a SOP from real world experience which is what COPA have done. As the evidence accumulates doubtless the recommendations will become more refined and statistically more reliable BUT no one will ever be able to safe the chute offers a guarantee and is ALWAYS the best alternative all that it might be possible to say is that statistically it is the best alternative. That is a very different matter.
So the chute doesnt offer certainty any more than a forced landing offers certainty - the only certainty on offer is an extra engine with enough power to enable the flight to be completed with a pilot competent to fly on just the extra engine while still relying on that engine to keep turning.