Most of the time source material doesn't correspond 100% with the model.
I know ... this also happens with the source material itself. Plan and pictures are not always corresponding.
By the way, the model is not cut in stone. If you need a chair 2 cm more to the front and a table 3 cm higher ... that isn't a problem to do, because it doesn't hurt the mapping.
To move a cutted window 2 cm would cause a remapping. But as you said, you can move them yourself, because they aren't cutted.