I hear you and I understand the distinction. The correct terminology would be inline helical/spur/planetary/hypocycloid drive. Or geared hub if it’s inside the wheel. Direct drive, by definition, means no gearing at all and the motor output shaft drives the wheel without reduction. But I digress.
I’ve done a good amount of reading on geared hub and mid-drive setups, mostly on Endless Sphere. You can get monster torque and power from a high-revving motor, particularly when you’re gearing down like 8:1 or higher. That kinda reduction just isn’t possible with belts unless you have multiple stages. High kV motors are more efficient with less cogging. One of the more extreme examples is the Tangent Motors mid-drive ebike setup with a beastly little Astro Flight 32xx inrunner mated to a cycloidal gearbox at 40:1 reduction, where it drives a chain. Insane torque.
As we push the limits of belts and move to bigger wheels, we get into territory of e-scoots & trikes. Those guys have been monkeying around with inline gearing for years.
I would love to see somebody mate esk8 wheels to the output shaft of a cycloidal drive. Maybe it’ll be me…