Well yes it’s true that geodata for PNG / New Guinea generally has lower resolution than some other places, but there is definitely much better elevation data available than MSFS currently uses, and also definitely much better satellite data in many regions.
The mesh appears to be based on SRTM (the Space Shuttle data from 2000) which unfortunately has many glitches (i.e. spikes and holes) in New Guinea - the same data used by OpenTopoMap. There are other DEM datasets around which don’t have those problems.