That will probably be the case, but there is the window reveal and the actual pane will be recessed by about 18 cm, thus also having this distance from the staircase.
Correct, the staircase is flush with the wall, it's only about the gap between the window and the wall/staircase. It shouldn’t sway, won’t be a single-beam like in the photo, but a saddled stringer staircase with risers and a stepped glass railing. We will request prices and depending on that, either use the railing with the window or a railing on both sides. The opening upwards is relatively large, so they can place it somewhat centrally.