I'm not sure why that youtube dood thinks there aren't already COVID-19 Emergency Temporary Standards in the CFR's, and why he thinks OSHA can't issue more. It's well within OSHA's legislated authority to issue new standards or change current ones. 1910 Subpart U is the current set of ETS's.
I don't particularly like the Bureaucracy's ability to just "find" stuff and add it to the CFR's, but as I was sadly educated when the ATF decided every damn thing may be a receiver, it is within most agency's power to promulgate regulations.
I'm sure that it will be challenged, and while I hope it is cast down, I'm not as confident as that guy that it will be.
I predicted to my coworkers this morning that OSHA would be how he did this, as they have a ton of regulatory power and leeway.