Small correction: the two known sons of Mrs. Elliott née Mitcheltree were William Elliott, Esq. and James Elliott.
William R. Elliott is an unrelated man who just happened to live in a nearby community in the same county and share very very close birth and death dates with my William. Which is something to watch out for when researching this line.
I suspect my ancestor appended Esq. to his name in the first place to differentiate himself from William R. And also, because "Esq." sounds cool. ;)