Same here, and now pretty common in all Risk Management Contingency Planning SOP's. Probably some regulatory driver dictated it.
All agencies do emergency planning, and a short term shelter in place contingency presumably ranks pretty high on the list of the sensible things that might make the to-do list. This is Treasury, which is downtown, right next door to the White House. I can think of 101 things that could make sitting tight overnight a pretty good choice.