Ok so you always connect additional tiles leading down to allready revealed tiles on that lvl? What if only one tile is available on lvl 2? Both stairs down lead to adjacent of eachother? Seems weird.
Yes, that can happen. Keep in mind creatures can only use stairs to go between levels (unless they fly), so having these other passages is just a help for the players. Also, bosses can use the broken stairs from level 3 to level 2.