The window will only cut a hole in the wall it belongs to - it won't trim other walls as well.
If you have walls butting up to the inside of the window, you will have to control the end position so they don't trim with the perpendicular wall (with the window), so they will not extend to the outside of that wall.
The easiest way would be to have those 2 walls in different layers and give each layer a different intersection group number (in the layer settings) so they don't trim with each other.
One of the forum moderators. Versions 6.5 to 25 Dell XPS- i7-6700 @ 3.4Ghz, 16GB ram, GeForce GTX 960 (2GB), Windows 10 Dell Precision 3510 - i7 6820HQ @ 2.70GHz, 16GB RAM, AMD FirePro W5130M, Windows 10