They wanted the mouse to have a name like “Microsoft® Wireless Notebook Presenter Mouse 8000” but they accidentally used the wrong encoding and the name was invalid. Because they already made thousands of devices without properly testing them, the “obvious” solution was to patch the Bluetooth stack on every single computer in the world to fix this issue. It’s the only Bluetooth device released in computer history that requires this.
I still have my X6, with the modular numpad you could stick to either side.
Although nowadays I only use it for my test bench at home. That thing was truly ahead of its time.