While I certainly wouldn't disregard the possibility noske brought up, I had a quick look back at the report because I was sure I was forgetting something - which turned out to be this:
Originally Posted by BEA Final Report (EN) p.169
The relief crew did in fact inherit some decisions to make. From 2 h 01, the PF mentioned the subject of the ITCZ, turbulence and the choice of flight level in his briefing to the co-pilot who joined him as relief for the Captain. From 2 h 04 to 2 h 08, after the Captain’s departure, the two co-pilots discussed the ITCZ again. The PF repeated his idea of climbing to level 360, without doing so. Acknowledging this non-solution, he warned the cabin personnel of imminent turbulence. After changing the gain on the weather radar from “calibrated” to “max”, the PNF then suggested as of 2 h 08 min 03 a route alteration, which the PF willingly executed.
Therefore there exists the possibility that the "problem" as you describe it - namely the weather/turbulence situation and how to avoid it, may have been considered as solved in the mind of the PF with the PNF's lateral course change.