Cook and colleagues expose a paradox at the heart of green infrastructure. The field celebrates multifunctionality, yet planning and engineering practices repeatedly isolate functions into disciplinary silos. Their review identifies fifteen green-infrastructure elements and fifteen objectives, revealing a persistent split between engineered systems associated with water management and more natural elements associated with biodiversity and wellbeing. The problem is not lack of possible benefits but the difficulty of intentionally coordinating them without creating an unmanageable design space. Multifunctionality becomes an epistemic coordination problem. The authors respond with adaptive design, explicit assessment of trade-offs, interdisciplinary collaboration and political commitment. The paper connects ecological design with decision theory and institutional organisation: urban green infrastructure performs multiple functions only when those functions are made visible early enough to shape design, rather than being retrospectively claimed as passive co-benefits.