Fascinating. I just looked up JAR-27 which is the certification code for helicopters up to 7,000 lbs. There is no requirement for them to give you PEC data or any climb data beyond that pertinent to either take-off performance, or determining the height/speed ceiling. It is a requirement that your ASI should be within 3%/5kn at any forward speed above 80% of climb-out speed. It's apparently not a requirement to compare this for climbing and descending flight - the implication (if not specific statement) of the standard at 27.1323 is that it only needs assessing in level flight.
As a flight test specialist it staggers me that they are allowed to give you so little performance data. As a certification Engineer, I'm pretty certain that they'll give you no more than the minimum that they have to.
G