To address a point not covered by the other answers, the only cases where I've heard of mass executions being plausible have been murder-piracy, and drug-related. E.g. in 2013
Four foreign men have been executed in China for the murder of 13 Chinese fishermen on the Mekong river in 2011, after being paraded on state TV. [...]
It is believed to be the first time in China's recent history that live footage of condemned criminals being taken to their execution has been broadcast.
Or in 2017
Lufeng, a city in southern Guangdong province, is increasingly publicising criminal verdicts, in what appears to be a bid to stamp out its reputation as a hotbed for synthetic drug production.
This week, a court in the city invited members of the public to watch 12 convicts be sentenced at a local sports stadium. It was attended by thousands.
Popular news website The Paper says that following their verdicts and with the approval of the court, the 10 who were given death sentences for drug offences "were escorted immediately to the place of execution and terminated".
But no footage of mass executions proper has transpired, as far as I know. (The YT video linked in the original question has been taken down, so I don't know what it was purporting to show.) On the other hand, Radio Free Asia has some footage on its YT channel purportedly showing one man being executed.
Likewise 4 Japanese (suspected yakuza) were executed in China in April 2010, again for drug trafficking. Such stories regarding mass death sentencing for drug trafficking (and probably serial executions) are not uncommon though; they go as far back as 2000, at least.
Apparently, such executions are sometimes even coordinated across regions, in order to have more impact on public awareness.