That is not a true statement. The further forward the main gear are positioned ahead of the CG the greater the tendency the aircraft has to ground loop. To far forward and it can be almost impossible to take off. As you move the gear closer to the CG the more stable the aircraft becomes, but it will have a greater tendency to nose over. You'll notice that models that come in for a landing that have the gear to far forward, the pilot cranking in lots of rudder to keep the plane heading straight, it does not take much movement either forward or aft to greatly affect the ground handling either way. It's up to the designer to find the sweet spot, that provides good take off and landing directional control with a reduced tendency to nose over.