First of all, who cares if it's "real" or "posed"? Honestly it sounds like it was somewhere in the middle. If it's not 100% real maybe it doesn't get to be called truly "street" but again, so what?
It works as an evocative photograph.
We're not disturbed by the the clean, healthy mom and baby putting arse to tarmac in a clean back alley. What we're disturbed by is the potential implications of the scene. The thing is simply littered with symbols of destitution, decay, drug use, and so on. The fact that the mom is apparently clean and healthy, the fact that they're pretty well dressed and equipped in first place does not make the symbols go away, and in the second place by conflicting with that fairly blunt basic imagery makes us even more disturbed.
If it was just a junkie in a filthy alley, we'd "know" what was going on (whether it was a real junkie, or a model, or a model who is also a junkie, or whatever was "true", the scene's internal reality would be clear). It's not, so not only do we have all these unpleasant symbols in front of us, we DON'T know what's going on.
With respect, it's kind of insulting to assert that other people who ideas that differ from yours must simply not have looked closely.