For electrostatic discharge testing, why do the standards connect the return cable to the ground plane? Is there any difference in test results between connecting it to the discharge gun holder GND terminal and performing the test?

For electrostatic discharge testing, why do the standards connect the return cable to the ground plane? Is there any difference in test results between connecting it to the discharge gun holder GND terminal and performing the test?

First, regarding the mechanism of the electrostatic discharge tester and return cable,
the method applies electrostatic discharge by creating a loop with the point connected by the return cable as the reference potential (0 V).

The reason for connecting the return cable to the ground plane is to secure a stable reference potential by using the large-area ground plane as the reference potential (0 V).
In contrast, the GND terminal of the discharge gun holder has a small area and provides an unstable reference potential, which affects the reproducibility of test results; therefore, it is not permitted by the standard.