Shawn, Nick
I may be the one of the examiners who is not an expert. Within the context of a practical test there is the aerodynamic explanation of IGE and OGE and then there is the performance explanation of IGE and OGE.
The main rotor diameter of the R-22 is approximately 25 feet (forgetting the 2 inches). The aerodynamic explanation of IGE is 1.5 to 2.0 of rotor diameter. The manufacturers IGE hover performance is calculated at 2 feet. I have been with applicants who happily explain that IGE hover height for an R-22 is between 37.5 and 50.0 feet less skid height, which is not wrong unless you are making a high density approach to a mountain top and you do not have Pilot Operating Handbook OGE performance.
I understand the difference between theory and practice. When it comes to a FAA Practical Test, and an IGE performance chart is being used to determine IGE performance, I expect an applicant to respond to the question "and for the purpose of this chart what is IGE performance?" the answer to the question should be what the manufacture has published. That may be a "flat earth" response, but it holds true in Lorentz four dimensional space-time with the same validity as the Special Theory of Relativity.