If by “design” we mean the user research, synthesis, narrative making, persona development, design strategy, interaction design, information architecture, content strategy, visual design, etc. Many of these elements need to happen well before code can begin. Most of this work needs to be done to understand the whole of the system that the parts will be built in. Can this process also be done in time-boxed segments? Sure. But they have to come before the segments where production is done. Any agile process that puts code even in parallel to design is giving design lip service at best.