I haven’t read the spec, but I believe that some backwards compatibility is built in, and there’s a degree of complexity involved in making a robust framework that isn’t general purpose (like Wifi), but instead offers compartmentalisation of different device types and use cases.

I agree with the manufacturer concerns, but many were in a bit of limbo while Matter and Thread languished in draft RFC hell. The spec was always ‘coming by the end of the year’, and obviously impacted by the pandemic.

At least now, there is some certainty and a path forward.