In terms of infrastructure you would be fine but some businesses have systems that need 12 hours or more to properly shut down.
If you have half an hour and your system will slag out it makes sense to ignore the 12 hour proper shut down and just flip the switch now!
The article makes mention of 20 - 30 hours from the event to impacting affairs here. They’re monitored fairly closely as I understand. Is there some hole in the assumption that it’ll be known with enough advance warning to at least mitigate the effects of power surge?