What do you mean it "pretty much stays the same"?

I can add 500 in state taxes or 5000 in state taxes and the tax on the 1041 stays exactly the same. 

Now if I input more state taxes than ALL the income on the return, the k-1 zeros out and the 1041 does get some benefit, so maybe thats what you see happening.

I'm not seeing any program defect here.