It could be another huge catastrophe if/when whatever landslide material is plugging the water to form the lake suddenly breaks open from erosion. Boom, instant humungous flash flood downstream....
Depends on what is in the landslide. If they have a lot of aggregate and rock, the landslide dam might survive for awhile.
Most landslide dams fail when they over-top; because they just happen and aren’t designed, they’re usually lacking some manner of spillway.
Any way you look at this job in China, tho, it ain’t good. Their river canyons are usually steep and narrow, which means that if the dam does fail, you’ll see some high water velocities going downstream.