So perhaps it should read
There are some pilots who use “settling with power” to describe vortex ring, in fact some publications use the terms interchangeably. Confusion results when symptoms are related that do not describe true vortex ring but rather describe “settling with insufficient power”. This may occur when a pilot attempts to arrest a descent only to find that he has insufficient power available to bring the helicopter to either a hover or a no-hover landing without exceeding the engine limits. However, this is not a vortex ring situation.
Another situation, ‘over-pitching’ is often misinterpreted as vortex ring. This is where the pilot increases collective and the engine cannot produce enough power to overcome the increase in drag on the rotor system. The result is that the rotor system slows down and loses efficiency causing the helicopter to sink. Again, this is not vortex ring.
Perhaps it could also add that overpitching is often experienced following the 'settling with insufficient power' as described in the first paragraph.