The rule does not state it outright, but you have said that the robot being pinned must take any opportunity to escape the pin, or else the pin will not be called.
For simplicity, let’s say that in this situation, a red robot is pinning a blue robot. If the blue robot has more torque and more traction than the red robot, and the blue robot could push the red robot away, would this count as an opportunity to escape the pin? If the blue robot chose not to push the red robot, would the pin be called?
Referees will be looking to see if teams are trying to exit a pin. If a red robot is pinning a blue robot, and at no point does the blue robot try to exit the pin, (e.g. it never sends power to its drive motors), this would not be pinning. However, referees should not be expected to know the torque and traction difference between robots.
Basically, if you’re being pinned, make it blatantly clear to the referees that you’re trying to exit the pin.