It’s a theory, but loading-related accidents pretty reliably happen within seconds of attempting to fly (see 747 at Bagram as an example), as that’s when the greatest body angles occur and where you are most vulnerable to shifting/wrong cargo, mis-set trim, etc. Also, I suspect manufacturers take fuel movement into account when designing loading limits; manual and automatic load sheets certainly take account of CG movement during fuel usage to make sure it doesn’t cause problems at any stage of flight.