Generally, any charts that are part of an approved Rotorcraft Flight Manual have all that IAS position error magic built in. The FAA and CAA are meticulous about the accuracy of procedural data as presented to the flight crew. For the S-76 and S-92 flight manuals, we must use TIIAS as the published data for Cat A procedures and climb data (TIIAS = True Instrument Indicated Airspeed, which is what would be read on an airspeed gauge with no internal error ).
Do you know that the Vy is actually 65 knots? Does your climb data support the possibility of error?