I would be very curious who at Bell said this. I have been told consistently, over the four years I have been flying a 407, and attending 407 recurrent at Bell, that the Vne in a 407 is a function not of retreating blade stall, but a durability/economy issue having to do with the useful life of components in the rotor system. An interesting feature of the 407GX is the red line moves with density altitude, and in bumpy air with airspeed fluctuations, you can get an overspeed warning like in a jet.
In the legacy 407, we used just under 140 knots TAS as a wag for Vne, but without the adjusting red line, I am sure folks momentarily exceed it in bumpy air.
It is not a coincidence that the Vne charts for the MD530F are mounted right in front of the pilot, and with any density altitude one might be surprised how slow Vne is. I learned this flying a 530F from the completion center to the factory, with a MD test pilot, when we were both surprised how "rough" the air was at 8,500 feet on a warm day -- until we finally looked at the Vne chart.