They use a grid of coils. By activating multiple adjacent coils, it behaves like one big coil. From a physics perspective it's really neat: the magnetic fields of opposing currents in adjacent wires should cancel. But the price you pay is that you have the charging current flowing through more length of wire, and more resistive losses (heat).

Phased array inductive charging. Fascinating!

21-24 is a weird range

As someone who knows basically nothing about designing electronic devices, my initial thought is 3 rows of 7 coils or 3 rows of 8 coils? This wouldn't make it a range, though, so much as an either/or situation.

Would probably make more sense to choose some hexagonal pattern.

Oh, good point!

It's a weird design.