Don,
I figured it out. terrain.cfg contains multiple entries for ORBX polys which are caused by there being potentially 27 flightsim geographic regions and that landclass, landclass polygon and vector features are all listed. So the TSPro indexing algorithm is correct. terrain.cfg just contains different GUIDs for where there is more than one fltsim region represented per ORBX LC. Sometimes there's two entries per distinct ORBX LC, but often there's three or more. The name= field in terrain.cfg in a roundabout way, shows whether it's North America North/default (B), Australia (G), Europe British (A), etc.. For example, some terrain.cfg entry name= contain "PNW" for ORBX NA Pacific Northwest, some say "AU" for ORBX Australia.
Unfortunately, you might want to forget about non-stock entries for the moment, unless you know someone who has decoded the revised ORBX lclookup.bgl, which matches up the terrain texture BMP filename codes with the terrain.cfg LC codes. You could parse through terrain.cfg and separate out the different entry types... thinking out loud here, maybe that is presently coded, but isn't working correctly.
Sorry for the rambling, but the unintentional mess that MS created between terrain.cfg and lclookup.bgl makes the two files like the early vaudeville routine (1903) of Alphonse and Gaston.
Jay