first of all welcome here in the forum and thank you very much for your report.
Yes, SimBrief uses exactly the same database as we use for the charts and the navdata updates. So, you can be 100% sure, that when you plan a flight with SimBrief you can use it 1:1 in MSFS and in all current (and upcoming) addons which are supported by us.
To your question about VISR:
There are airports included in the source, which have no runways and VISR is such airport. You see this also in the charts-app:
So, it makes no sense to add an airport for flightplanning, when you don´t have any runways and therefore such airports are not selectable in SimBrief. For many, many, many years (I guess 6 or 7) we have decided for the navdata-updates to merge FSX runways with the airports where the runways are missing but thats only for the navdata-updates, not for the charts nor for SimBrief. It´s a own merge in the navdata-parser which works completely independent.
After so many years, it makes also no sense to implement this merge in SimBrief because the runway-idents can be outdated (due mag var), closed or similar else. The FSX data source is simple too old for such merge.
Last, the reason why there are airports but no runways in the source is, that there are no official information existing from the government of such countries.
Hope that helps,