That's the thing, I get the BPA but positional value factors in as well.
I think the truth is that our team didn't have Slater or Fields rated higher than Horn. I definitely see the attraction to Horn, much more so now that I have seen so much more information on him post-draft. I even see that he is likely the best of the first round CB's. But....will he be better for us than Fields or Slater? TBD.