I think I would agree with most of what you state
jno with the exception of two of your inclusions... the first being the use of the word"embellishment" as a pejorative... I think it's more realistic to understand a later writer, as you infer, simply wished to clarify which
Ur was referenced, since there were several and by 400 to perhaps 800 B.C. the Chaldeans
were prominent in the Babylonian Ur. Secondly, your statement that "...they got it wrong..." extensive, qualified scholarship and on site investigaiton indicates the probablility of the Babylonian Ur as being the one referenced in Genesis (as well as Nehemiah 9:7)...
space doesn't permit a full presentation of the evidence, but here a link to a well written document supporting the Babylonian location:
http://fontes.lstc.edu/~rklein/Documents/Ur.ht m