The oxy bottles on a 777 are composite wrapped pressure vessels (COPV) which are designed to leak before bursting. The only COPV failure that I am aware of is in the US space program which uses much larger, lightweight COPV's that differ significantly from the type used on the 777 in both design and purpose, storing cryogenics for example.
If a COPV's onboard MH370 did somehow explode, the resulting failure to record the event by the CMC would need to be explained. The bottles sit near the LH AIMS cabinet but are not in proximity to the RH AIMS cabinet, and the bottles are oriented with the tapered end, the most likely failure point, pointing toward the rear of the aircraft. This setup would propel the COPV forward and away from the electronics in the event of a bottle explosion; something the COPV is designed not to do.