I got this by PM from the developer of this product; he was concerned about what he saw as inaccurate coverage here
We are not using SRTM. Originally we were but it just covers 60N to 60S. So we have had to purchase worldwide data from another source.
Also we have European and US IFR enroute, approach and aerodrome charts loaded in the program so it is not VFR only.
To date we have over 200,000 lines of source code written and the terrain is a very small part of it. The flight planning and aviation databases are the biggest part.