OOh I can answer that one since it’s a conversation floating around Lemmy ……
There are different standards for apartment buildings, where US building code requires two means of egress and it can’t be a window if over a certain height (3 floors?). American apartment buildings will have two staircases (and the argument is you could have fit another apartment in there) whereas some other places might require only one (where the argument is modern technology like smoke alarms make the second exit less necessary)