Delivery of fonts aren't what's used to track people. Rendering of fonts is. Different machines render fonts in a unique way. Consider different GPUs (hardware

Delivery of fonts aren't what's used to track people. Rendering of fonts is. Different machines render fonts in a unique way. Consider different GPUs (hardware differences), different drivers (kernel/driver differences), browsers (user-land differences), and sizes (user settings) can all contribute to a font being rendered differently per-user and increasing entropy of a particular unique font id.