The GEOSIntersects function is too strict for our purpose, a snapped point can be considered as not on the line by GEOS (as can be seen when the start or end of the splitting line is snapped to a line, sometimes it splits the line, sometimes it doesn't). This was an issue in the first version when splitting in the middle of a segment.

However, as we are now restricted to the vertices, the coordinates should be identical, so it can be put back.