Yes, I had seen that a few weeks ago.
I have no idea what their structure is behind the scenes, but they probably
downloaded the language code table and the macrolanguage mappings table
from the SIL website:
and plugged the data into their processes.
These two tables (+ the data on B/T identifier equivalents compiled from
the ISO 639-2/RA site or from the sil site) contain all the data that they
would need to create the language codes part of the table displayed as
part of any entry on a language.