Excerpt from change request document:
Monpa (or Moinba) is a cover term meaning "man of the lower country" and is used to refer to several ethnically related peoples which may not be related linguistically. Andvik states "The Monpa label is unfortunate, in that it separates languages which should be grouped together, while joining under a common name languages which should not be grouped together." Other publications (listed below) have indicated high variation in language among the Monpa groups we had previously listed under Moinba [mob].
Survey in 2005 has helped us sort out the various groups. The highest lexical similarity percentage among these 5 varieties are Chug with Lish - 62%. Informal comprehension testing indicated that Chug speakers had difficulty fully understanding a Lish story. The next highest similarity is Kalaktang with Tshangla_tsj - 62 – 71%. Kalaktang speakers averaged 55% intelligibility of a Tshangla RTT with high standard deviation. Lish & Chug with Tawang and Kalaktang -15-21% LXS, Kalaktang with Tawang - 26-28% LXS. The closest language to Sartang is Sherdukpen with lexical similarity 49% to 60%. Sartang is less than 32% similar to the other 4 Monpa languages. Although I personally doubt the accuracy of the LXS numbers, they do indicate a great deal of variation which confirms similar statements by published sources.