Yeah, targeted exercises don't do a thing to reduce belly fat. Ask any heavyweight boxer or MMA fighter who comes in overweight but still has rock hard abs... under the flab. Nobody ever put down Big George Foreman with body shots, not when he was young a chiseled, not during his comeback in his 40s when he looked like the Michelin Man some fights. Despite looking overweight Foreman was known to be diligent about training and was tough as a tank under that fat.
Insulin and cortisol appear to have some influence on stubborn belly fat. Insulin can be controlled to some degree with diet. Observers of bodybuilding have described differences between Schwarzenegger's era and today, noting that more bodybuilders today have more belly fat. This has been attributed to the deliberate misuse of insulin. And it's not just subcutaneous fat but interstitial fat around the intestines. Very difficult to get rid of.
Cortisol is trickier and it appears to be linked to stress. It may be difficult to lose belly fat, even for otherwise fit and slender folks, if they have a lot of stress for whatever reason. And if the body feels "stressed" by efforts to lose weight -- changes in diet and training, including fasted rides to provoke burning fat -- it's possible the body compensates by hanging onto belly fat.
I found it relatively easy to lose 50 lbs with sensible changes in diet and exercise, nearly eliminating beer and alcohol, cutting way back on sugar and junk carbs. But the remaining 3-5 lbs of belly fat is stubborn stuff. I'd have to go full keto and switch my bike training to almost exclusively low and slow, zone 2 stuff endurance rides, including fasting rides as much as I could tolerate. I'm not sure I'm motivated enough just for 3-5 lbs. I'm not really training for anything, just trying to stay fit and improve a bit. But if I get serous about time trials again, I'll consider those changes in diet and exercise.