The FBA comparison is sharp, but there is another layer here: Shopify is capturing the data feedback loop.
When non-Shopify merchants route through Agentic Plan, Shopify gets visibility into AI-referred traffic patterns and conversion rates across platforms they do not own. That is intelligence they can use to improve their own infrastructure.
The MCP angle matters too. If Storefront MCP becomes the standard for AI-agent-commerce, Shopify controls the protocol. That is platform power at its purest.