When I worked on the Thor books, we used record proofs (I think that's the name) of the art which were photographs of the original art taken prior to the last editorial changes prior to publication.  We also used these for SHIELD - that's how that famous shot of the woman's behind which was altered in the final books made it to print this time.  I would imagine some of the Syd Shores books exist in that format - so it might be possible to extract more from the line work, but who knows - maybe they already did that and this was what came out of it.

I think the intention of assigning these books to Shores was an effort to replicate the Golden Age feel of Cap as Shores was an artist on the book at times.  It does manage to echieve that effect, though I prefer Giacioa.