I think their idea is you should use a wireless mouse. Notice that the "Fully equipped for a wireless world" heading appears above the mention of USB-3. Indee

I think their idea is you should use a wireless mouse. Notice that the "Fully equipped for a wireless world" heading appears above the mention of USB-3. Indeed, putting only one port forces the issue, because I imagine a significant amount of the time, if you're using a mouse, you're also plugged in to power, and now you can't do both without a hub of some sort. Reasonable people can disagree wrt whether a wireless mouse is acceptable for their use case, of course. Just like reasonable people could disagree when Apple stopped shipping devices with floppy drives and (later) optical drives.