The problem, OP, is that what you're claiming (the child stands there for hours, the child is never taken out, the child wears inadequate clothes in winter) contradicts what you're stating (you only ever see the child for a brief moment walking by, you only ever see the child indoors). It's hard to reconcile those contradictory statements.
There is simply no evidence of anything "not right." There could be any number of psychological reasons why the OP has fixated on this child. MN puts great store in the idea of "trust your gut" but studies have shown that all kinds of subconscious biases and memories influence "gut feeling." (There are plenty of people whose "gut instinct" is that every black kid is a threat.) It's quite possible something about the house or child is triggering some kind of unconscious traumatic memory, and that's why the OP finds looking at the child upsetting.
I feel a great deal of sympathy towards the posters who were abused and neglected as children, but there is massive projection going on. People saying "My kid stares out of the window" are not projecting, but making a simple statement of fact, ie pointing out that staring out a window is a very normal thing to do.
False SS reports CAN cause harm. They take up valuable resources, and in extreme cases can harm families. (I really don't understand the posts claiming that a mother's mental well-being is somehow totally irrelevant to the safety and happiness; a mother's emotional stability is essential in raising children!)
Okay imaging this (hypothetical, but based on real experience) scenario: the kid is perfectly healthy and happy, just likes to look out the window for his favourite doggy every afternoon. But his mum grew up in care and had PND, which means she's "known" to SS. Normally they'd ignore "I saw a kid looking out the window" but because the mum's already on their radar they go round. She's struggled her whole life to get over the stigma of being in care, having SS round just because her kid likes to look at doggies causes her to suffer depression and anxiety. Meanwhile the neighbours saw SS visit and start gossiping. Maybe the gossip causes her to lose work. Maybe it causes family discord. Maybe marital problems ensue. Things get worse from there.
You could just as easily damage a family as save an abused child.
I am saying this as a survivor of familial child abuse, and I am also a registered child chaperone who has had child protection and sign of abuse training.