Opinion: To the point - Why not make a fuss?

I am sitting at the desk by the front door of the nursery where I'm the head, and I hear crying, then a clatter of doors. A mother comes past, glances at me and says 'oh no, I timed that all wrong'. She had settled her little boy in with his key person, she explains. He was playing happily and she started to move away. If she had just left then, it would have all been alright. But she had waited a few more minutes, then he had looked round at her and become distressed...