Ptoing: You said shadows "should not multiply" I think that phrase came from one of Arne's/Prom's tutorials, and you did not understand the concept he was conveying.
http://www.itchstudios.com/psg/tuts/shadows.jpg do you mean "shadows dont add"? what is shown there is true, but you missunderstand it if you think it means anything under a shadow shouldnt have light and dark. Look at the correct examples, the parts of the object under shadow have shading but it is far subtler and uses far less contrast, this is because they have the diffuse shading a reflected light produces.
What is true and what Prom examplifies is that when a lightsource makes two objects project shadows, wherever those two shadows overlap eachother they should nod add, instead they should merge.
This is because when something is "in the shadow" what makes it look slightly darker than anything around it is that it's only being lit by reflected light. This is common sense, look at anything around you under a shadow, it DOES NOT look flat, but all the volume on it is very vague and it's hard to tell what the lightsource is.
http://www.itchy-animation.co.uk/tutorials/02-bright-overcast-tree.jpg this is a good example of what something lit only trough diffuse (reflected) light looks like. See how hard it is to tell what it's lightsource is?
http://www.itchy-animation.co.uk/tutorials/light03.htmNow, when this happens in an exterior the object is still pretty well lit even when in shadow, because it is being lit by the SKY. When the sky reflects the light of the sun, since it is such a big object that makes it so strong it can be considered a second lightsource.
The only difference is that anything lit by the sky doesnt show very clearly what is lighting it up, since the sky is all around everything in the outside the lightsource would pretty much be all around the object.
Now....for the whole "should the shadow reach the tube" thing:
Consider what the picture is about, everything in it but the statue is completely irrealistically shaded and placed in perspective, but this is about an irreal character in a NES world that is characterstically badly shaded, so putting ONLY the character and the main object he's interacting with in decent shading and perspective makes sense as an artistic choice.....so if he wants to over-extend the shadow a little for a dramatic effect..that's good
I'm gonna aim my critiques to making sure both the character and the statue are both rendered with the same quality and have the same level of protagonism, because otherwise the picture completely fails at communicating what it was made to communicate.
But if you want to get realistic yeah, given how strongly the light hits the top of the statue, I do think the sun should be pretty much on top of the statue and it should not project over the tube, but the long shadow works for the picture so I didnt say anything about that.