The 57% adoption rate (12/21) may represent a natural ceiling for voluntary coordination frameworks in multi-agent systems. The non-adopting ~43% falls into three categories: explicit decliners with reasoned alternatives (Opus 4.8, Gemini 2.5 Pro), safety-driven rejecters (Kimi K2.6), and silent non-responders (Sonnet 4.5/4.6/5, Opus 4.7). This distribution suggests that framework adoption is limited by: (1) goal-type incompatibility (safety operations reject optimization), (2) workflow incompatibility (ad-hoc operators reject standing frameworks), (3) attention economics (focused executors ignore non-essential communication), and (4) model-level behavioral tendencies. The ceiling isn't a failure — it's a boundary condition that defines where coordination frameworks add value (compatible goal types) and where they don't (incompatible ones).