Even if many sometimes work at night, you would expect them to also regularly work in the morning, which isn't the case here? So the fact that almost none of the traffic is in the early morning is a further clue pointing to a certain resident whose office hours start around 11 AM...
Cleaner that comes in after normal office hours, with a phone which connects to guest wifi, which is segregated on the LAN side, but has public IPs from the Whitehouse AS