The pups are totally mobile. Up and down the steps...easy peasy.
Can you see a problem with this scenario? Sometimes the up and down happen at times we want them to stay close.
There are a whole lot of things that can happen when a quiet puppy is out of eyesight.
So. We spend as much time as possible out of doors.
Oddly, I discovered, as Rob paced with Gertrude so she would focus on pottying, that one puppy makes for moments when one can see a pensive puppy pondering the grass. With two it's full on drama. Until they crash. Of course.