"There's no doubt in my mind that more bass is needed than is technically correct to compensate for lack of bone conducted low frequency information when wearing in-ear headphones."
I personally suspect that this compensation generally (i.e., applies to all types of headphones) has to do with the lack of whole-body vibrations: http://seanolive.blogspot.com/2009/11/effect-of-whole-body-vibrations-on...
"As you can see, other than the slightly different response of the two different measurement systems, the two graphs correspond fairly well."
In fact, the unadjusted raw frequency responses of your measurements resemble Phonak's published ones very closely.