Is the method for losing upper and lower belly fat different?

It has been quite a while since I started my diet, and my weight is decreasing little by little. However, I am worried because, strangely enough, my lower belly is particularly hard to slim down compared to my upper belly. My upper belly seems to have flattened out somewhat, but the area below my navel is still bulging out, so it is very noticeable even when I wear clothes.

I consistently do cardio exercises and work hard on my diet, but my lower belly seems to show almost no change. People around me say that the causes of upper and lower belly fat are different, and some suggest it could be due to posture, pelvic issues, or weak abdominal muscles. I am curious if that is really the case.