Instantaneous velocity and instantaneous rate In the VT diagram, when the limit is removed, why can the instantaneous displacement and the distance be regarded as equal?

Instantaneous velocity and instantaneous rate In the VT diagram, when the limit is removed, why can the instantaneous displacement and the distance be regarded as equal?

In the case of instantaneous displacement, the track can be regarded as a straight line, and the instantaneous displacement is equal to the distance, rather than equal to the distance