The guy just did not connect the dots - the headset works with other devices - it does not replace them. That was the point of the integrated system between devices. It needs the other devices to function in many environments, and will never replace high-end Macs (or PCs).
You are correct. It is an addon.
It does replace them, unless you also want to hold on to your existing devices. It's powered by an M2 processor which also powers the latest Macbooks and iPad Pro's so it can run all applications natively inside the headset.