Actually, the max speeds are correct.  Airliners.net is wrong, not only that, but flat out wrong.

The speed they show is the TRUE airspeed (or the speed the plane is travelling over the ground if there is zero wind).

Because the airplane is travelling at a higher altitude in thinner air, the INDICATED airspeed is much lower than the TRUE airspeed.  As such, the VNE (Do not Exceed Airspeed) is much lower than most people think since the airspeed indicators work off INDICATED airspeed.  Although, using VNE above approx. FL210 is incorrect as well as above that altitude, the speed of sound is the limiting factor because the VNE is in excess of the VMO (Do not Exceed Mach number).  VMO on the 727 is 0.92MACH, so at whatever altitude that 395KIAS = 0.92MACH, VMO becomes the limiting speed.