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I missed that when getting started so I recently bought some Sterling WorkPro 12.5mm which meets the spec. Compared to the Samson Voyager and Vortex I've been using it's not nearly as supple and easy to knot. The WorkPro is VERY resistant to twisting, and you'll end up spinning as you climb if there's any twist in the rope between you and the TIP.
Those minor complaints are easy to brush aside as the WorkPro is noticeably smoother and more consistent going through the ZZ. If WorkPro's performance is typical of ropes meeting the spec, it's easy to see why Petzl recommends using them.