This is not one whit different from the socialist utopias. The socialists also condemn high interest, medium interest, low interest, any interest. Their Kingdom of God will also be established when there is no more interest to be paid. There are moral legislators who today know less about sound principles of legislation than Moses did 3,300 years ago. Van Tuinen does not indicate what he might consider to be usury and what he might consider to be proper interest.
Nobody can define that.
It is impossible to have any standard on what is too high or too low an interest rate in a moral sense. Such legislation can be described as legalized casuistry. Any attempt for a clergyman to define usury as being too-high an interest rate is casuistry. They have insisted on avoiding sumptuary laws and other manifestations of casuistry. Casuistry is completely foreign to the genius of Calvinism.