I believe that is a standard part of the testing process. I remember seeing a 777 doing the same thing - an aborted takeoff then continues to the end of the runway with brakes on full, against engine power. The brakes caught on fire and burst the tires but they have to be able to taxi clear of the runway and last 5 mins or so on fire before the fire appliances in attendance are allowed to put them out.
Actually, I've not seen what you describe.
When a rejected takeoff test is done during the aircraft certification, there is more than just one thing being measured. The airplane’s maximum gross weight is computed, and the amount of kinetic energy that each wheel, brake, and tire assembly must be able to absorb is determined. Then there are a series of tests conducted (Kinetic energy tests) that demonstrate that the number of wheel, brake, and tire assemblies available (16 on a B747, 12 on B777, 4 on a B727, etc.) will be able to absorb the kinetic energy of the airplane under three (3) conditions; a full stop at maximum gross weight for landing; a full stop after ground acceleration to the critical engine failure speed; and what is known as the most severe stop – conducted at the most critical combination of airplane landing weight and speed.
Some of these data are gathered on a dynamometer – a rather sophisticated piece of ground test equipment – specifically designed for these tests. Some of these data are gathered “the old fashioned way” – via flight testing of the airplane.
The only accelerate-stop test that must be conducted at a specific brake wear state is the maximum brake kinetic energy demonstration, which must use brakes that have no more than 10 percent of the allowable brake wear range remaining. The accelerate-stop test runs are conducted at weight and speed combinations that will provide an essentially even distribution of test conditions over the range of weights, speeds, and brake energies for which takeoff data will be provided in the Airplane Flight Manual. And, of significant importance, the maximum brake energy “accelerate-stop” demonstration has to be conducted at not less than the maximum takeoff weight; it has to be preceded by at least a 3-mile taxi with all engines operating at maximum ground idle thrust; AND it has to be preceded by at least three full stop landings, using normal braking.
Graciously, following the maximum brake energy stop, it is not necessary to demonstrate the airplane’s ability to taxi – as, sometimes, it won’t be able to do that - which shouldn't surprise anyone.