from Captain Bob about offset:
It doesn't matter. Everyone does it. Parallel Track. It has nothing to do with what happened.
You seem to be unfamiliar with oceanic airspace navigation rules. Prior to the introduction of Strategic Lateral Offset Procedures (SLOP) the only authorised navigation was strictly on the cleared track. Without describing history and justification of SLOP which would be a bit out of topic, navigation is now permitted either on track, or 1 nm right of track, or 2 nm right of track. Application of SLOP does not require ATC clearance. Other rules apply for emergency situations and weather avoidance to cope with the fact that HF communications generally do not allow immediate delivery of ATC clearances.
Has the 3 nm left cross track error (XTK) reported by ACARS at 0210 something to do with what happened? Well, I would say that it depends on what happened exactly, what caused the crash.
Allowing for FM / GPS difference, rounding, ACARS transmission delays etc ... this XTK shows with certainty that AF 447 was steering off track when the AP disconnected and this was not in application of SLOP. Since I do not see why they would be doing so unintentionally or for no reason, I believe they were performing weather deviations. Whether these deviations were pertinent and appropriate I don't know at all.
Among possible hypothesis, perhaps the crew shifted their focus from weather avoidance to unreliable airspeed procedure/alarms and then inadvertently hit a convective cell and lost control. By the way, what would you qualify as the main cause of the crash in this case?