Jawbone, I am not sure if I am catching your point. What problem are you seeing with Welch continuing ideas first put forward by Hill? It seems most anybody could review the Book of Mormon and speculate it could have happen in such and such a place. There are several possibilities but they are limited enough in number that different writers will end up sharing the same speculated locations.
Even though Hill and Welch are part of different church organization they both share the same sort of hope and fascination with the Book of Mormon.It would appear to me to be normal and unsurprising they share a theory of location. Hill published first. That ok as far as I can see.