How does moving offices help when the virus spreads through people?
If you read the article it's about separating people.
The more office spaces you have, the more you can divide people into isolated groups.
It confuses the virus. If on top of that the office’s location is secret, it’s even harder to figure out for the virus where your employee are hiding and so if it can’t find them it can’t infect them. Don’t worry, people at the top know what they’re doing, just keep doing your job and don’t worry about the specifics.
After 9/11 the company I worked for (Silicon Valley, 10.000+ employees) had a truck with desks for engineers in case of emergency. Own power supply of course. Like a full evacuation or fire or earthquake at the main campus. I've never personally seen it on the campus.