By what metric does Spotify decide whether a device is a phone or tablet?

Granted, the line between "tablets" and "phones" has been blurred for years, and there is no universally agreed upon distinction. However, I am curious what metric Spotify uses to decide whether to call a device a phone or a tablet. Most people would call my OnePlus 7 Pro a "phone", yet Spotify identifies it as a tablet: What metric is used here? And why?