What does 'vet recommended' or 'WSAVA-compliant' actually mean for cat food?

Specialist-community discussion repeatedly points to WSAVA nutritional guidelines and brands that conduct feeding trials and employ qualified nutritionists. Brands like Hill's Science Diet and Purina (ONE and Pro Plan) are frequently cited in r/CatAdvice and r/catfood as meeting these benchmarks, which is why they appear often in vet-office recommendations even when ingredient-grading sites rate them lower.