The goal here is to find a criteria under which you can require that manufacturers open up general purpose systems. And the proposal is that a system that is Tu

The goal here is to find a criteria under which you can require that manufacturers open up general purpose systems. And the proposal is that a system that is Turing complete is also general purpose. The relational model is hugely expressive, and yet it is not Turing complete. So you have something that is plainly general purpose, but would be exempt from such a law. That you can modify the relational model to make it Turing complete is irrelevant, it's already hugely expressive. And that you'd typically run it on a machine that is Turing complete doesn't save you. If a manufacturer wanted to bypass that restriction, they'd design a system that is entirely dedicated to it.