Version of events (1)
Tang Qi knew his talent well. He had a top-tier orange core when he was in the core formation realm but originally when he broke through to the core formation realm it was a low-tier orange grade core.
The change only happened when he stumbled on an amber frost orchid sap in some ruins he was investigating. It improved his core by a small grade which was a huge boon that helped him reach the peak of the core formation realm.
Tang Qi was self-aware that given his talent, even reaching the peak of the core formation realm was purely by luck, so he was stuck in that realm for over 500 years. He had resigned himself to that fact, but he decided to risk it one last time and went diving at the shores of the Millionsfold treasure ocean, despite the infamy it had of cultivators easily dying to the mysteries within or to other cultivators.