Neither is dt / dt.

Velocity has units that are length / time — like miles per hour, or meters per second.

dt / dt is the pure number, 1.

dt/dt = 1 is a mathematical tautology that tells you nothing about the properties of the real world.

It says that time changes at one second per second, which is as true, and as useless, as saying that length changes at a rate of one meter per meter.