I'm trying to import points and lines, with altitude, using BeginBinaryImportAsync, however the altitude doesn't seem to get imported.

The easiest way to verify this, is to change the TestData in GeoJSONTests to look like this:

        new()
        {
            Geometry = new Point(
                    new Position(longitude: 1d, latitude: 2d, altitude:3d))
                { BoundingBoxes = [1d, 2d, 1d, 2d] },
            CommandText = "st_makepoint(1,2)"
        },

and run the 'Import_geometry' test..... It'll fail
also if you check the db, you see a point with only longitude and latitude:

POINT (1 2)

TIA

/Søren