from TFA "The company is also going fully remote, Dohmke wrote, telling staff they’re “seeing very low utilization rates” in their offices."

You're reading too much into the office closures. GitHub has basically always been fully remote and only a minority of employees have ever even seen one of the offices outside of occasional team meetups. Practically, all it means is that the employees who sometimes worked from the offices will have to find a co-working space or just work from home all the time.