Toyota isn’t expecting you to capture all the coolant any more. That’s why the first maintenance interval is ten years and the subsequent intervals are five. They expect the system with 100% fresh coolant (installed at the factory) to last ten years, but after that the expectation is that you only drain and refill the radiator so there is not 100% fresh coolant in the system ever again.
Draining and refilling the radiator is even easier to contain than performing an oil change.