I feel the heart of this article is here:
For many designers, the process often feels like an effort to design an engine, wheel or windshield without really knowing in what kind of car these parts will need to be integrated.
If people are designing in sprints without a clear idea of what they are building then something has gone horribly wrong. I think Agile works best when you have a clear understanding of what you're trying to do. If a design strategy hasn't discovered this in Sprint 0 then I think there will be ongoing problems.
Maybe I'm wrong, but I feel that the whole nature of Agile is that at the end of a sprint you've got some self-contained feature working. I don't think their is anything in the agile philosophy saying that what you have in sprint n will continue to exist in spring n+10. Like code you may refactor as more information comes in. As designers we need to accept that when designing in Agile that what we do 2 weeks ago may not exist tomorrow.
I think as designers that's a hard thing to do because we don't like 'waste', we want to avoid re-work and we also like to design the best solution with ALL the information we can get, but doing so requires a lot of upfront thinking and is just taking us back to waterfall.