Gerard C, of the three other flights on the track that BEA references, the LH reported moderate turbulence and deviated to the west, the IB chose to deviate 30NM to the east, and said conditions were severe. AF459 deviated 20 NM to the west, then chose to deviate 70-80 NM to the east of the track. (The summary of AF459 indicates they encountered unexpected turbulence at NATAL, and immediately began adjusting their radar, but there is no further mention of conditions they encountered, only what they saw on their radar.) So I don't know how you conclude that going in one direction off the track produced a smoother ride. (AF447 deviated slightly to the west.)
EMIT, as noted in the BEA's first interim report,
the BEA made a list of flights close to airway UN 873 during the night of 31 May to 1st June 2009 and asked crews for testimony. Not all of the information requested has been received at present. The testimony summarised hereafter is representative of the information already analyzed.
The narratives of the other flights as published by the BEA are incomplete, and the BEA has not yet provided any additional information. The BEA has also chosen to not release transcripts of the other flights' communications with ATLANTICO. Are there descriptions of conditions being encountered in their communications with ATLANTICO?
(The BEA summarizing seems to contain at least one error: the LH is said to be at FL 350; but the AMDAR trace says 325.)
I agree we have to await the full CVR transcript to see how situationally aware the flight crew was of the weather they were encountering. For example, did they adjust the mode and tilt of the radar, as AF459 did? If they had, and there was discussion of such on the CVR, would you think the BEA might have mentioned that in their most recent note?