Exposing abdominal muscles is not only for reducing fat, but also for strength training at ordinary times, because in strength training, it is necessary to tighten the core and abdomen every time. The higher the training level, the more abdomen is used and the clearer the abdomen is!
If you don't have strength training and just do aerobic exercise to reduce fat, it must be that your sebum is particularly low, and you may not have abdominal muscles! But such opportunities will be less!