Yhh, I was just about to say. They must have used a dual cell to accomplish this. As there's no way they would be able to transport their phones via air with a single cell battery of that size!
OPPO recently launched its Find X9 series, featuring a major upgrade in battery capacity, with the Pro model hitting 7,500mAh. If you feared about a potential reduction of these cells in global models, recent EU Energy Labels confirmed the Find X9 series will retain this impressive capacity in international markets.