Q: Why does the BRIR not correspond to what I see in the reflectogram and why are the differences between right and left ear in

A: The reflectogram and the reverberation curve is shown as sound pressure level(dB) as the BRIR is given in pressure (P). P is a more sensitive measure than dB (10*Log10(p^2)), and therefore the BRIR shows small details more clearly. Also BRIR has all frequencies included in the response at the same time. And especially the low frequency contribution that are almost not audible can have a strong visual influence on the BRIR.
Due to the sensitivity of the BRIR also the differences between right and left ear can seems very strong compared to what one would expect from two measurements so close together.
Even when source, receiver and room are all ideal symmetrical there will always be a small difference between right and left ear due to the calculation method for sound distribution used in Odeon.
Finally the HRTF´s used in the BRIR calculations will be shaped to contain some asymmetries.