[US_GRANT]

In real life I made my living as a general aviation A&P mechanic for several years, and also used to fly small aircraft occasionally. The only times I've ever seen chocks intentionally left blocking the aircraft's wheels during engine start and run-up were when testing the engine(s) for maintenance work. If the pilot expects to actually go anywhere, he removes the chocks before engine start. Brakes are perfectly suitable for holding the aircraft in one place, even at full throttle.

That's for small civil aircraft anyway. Military may do things differently.

Speaking as a military (OK EX military) Acft mechanic, we used to keep chocks in place until directed by the pilot to pull them so he could taxi out of parking. It was used partly as a safety measure in case he bumped the throttle(s) or an engine malfunctioned and started running up on it's own.