In that video, the X overheated and the processor was throttling. The AnTuTu score is about 50,000 points lower than normal.
It was basically in low power mode, so yes, it would "beat" the 8 Plus in that case. In every other battery test, the 8 Plus outperforms the X.
The non-stop looping tests on YouTube aren't representative because it quickly overheats a phone. Bigger phones can survive the heat so they continue to perform at maximum speed which in turn drains the battery. Small phones throttle down and reduce power consumption.