Yeah, actually no mistake per se in your labels, just could use the clarification. Thanks for the link, looks like good reading. Skimming a bit, here's the relevant bit:
Diffuse Field – The HRTF when sound is coming at the head from all directions simultaneously.
Independent of Direction – A rather recently developed HRTF to measure real world sounds in less abstract and highly conditional situations than the two cases above.
I would prefer to have an HRTF calibration curve for the special conditions of two speakers placed 30 degree of axis as that is what the headphones are trying to simulate, but no such calibration exists. After lengthy discussion with the applications engineers at Head Acoustics, the Independent of Direction HRTF was picked as the most applicable for my purposes.
And something else I found: