You say that as if it’s weird to call an iPad a mobile device. Would you say that a tablet is not a mobile device? What do you define as mobile device, and what devices would you use to determine if a web site is “mobile friendly”?

The common definition of mobile device is phone or tablet. The common definition of laptop is computer. These despite the fact that phones and tablets are computers and despite the fact that laptops and even desktops can be moved. It’s pretty easy to find lots of examples of the common definitions. Here’s a good one: https://en.wikipedia.org/wiki/Mobile_device