Aside from the fact that Xiang Ziyu had cultivated a modified version of Thunderbolt Proficiency, an abnormal Thunderbolt Proficiency, Little Beiyan's cultivation of the same divine power was slightly more advanced.
As for the Flame Divine Power, many more of his disciples and connected individuals truly practiced that.
Yan Yourong, being of the Great Five Elements innate holy physique, naturally cultivated the Fire Technique. Little Bei, while cultivating the Thunderbolt Proficiency, similarly trained in the Flame Divine Power; after all, one of his special phenomena was a bizarre Flame Evil Chicken.
Yi Sheng, with his True Yang Immortal Body, practiced the Fire Technique.
Even Li Ke, whom he had previously mentored, cultivated the Fire Technique.
Although Thunderbolt Proficiency alone could not amass a Golden Core, the Fire Technique could easily fill two Golden Cores with no issue.