Thats a weird statement. Happens on long haul flights. Most airlines even add some sort of warning to the weight and balance like “requires taxi fuel burn”. I have never noted anyone not waiting since everything on a modern aircraft is recorded and saved somewhere. The FAA actually audits a percentage of international flights. I had a friend violated for being 400lbs under his required redispatch fuel at the RDP. He climbed early for weather prior to the RDP which put him under the required fuel but he knew he would gain it back at the flight planned step location. FAA audited his flight and was not amused he continued to the destination airport.