would have thought so, even using light weight materials, brushless motors rely on magnets which are heave and batteries are light either lipo batteries, but i am pretty sure the high end bike like that do have to have a min weight, even though the manufacturers can make em lighter, so maybe they just make the bikes as light as possible and instead or putting in ballast weighs around the bike the have the motor????
Yeah just looked it up and a Tour de France bike has a min weight of 6.8kg and many added weight to make min weight.