I am not familiar with MBs warrantee on batteries, but I am relatively sure that the battery was the sole cause of the problem. The battery should be vented but a bad circuit inside caused the spark, I'm not sure what caused the gassing, probably the bad circuit (internal).
Your greatest concern now should be the total neutralization of the battery acid that got all over the area. I would ask MB to warrantee all carpeting which is destroyed by the battery acid. Unfortunately most of the real damage will occur over time especially if the acid isn't neutralized. I've seen holes basketballs could fall through due to battery acid spillage not delt with properly.
Owner 24 bay BSC
Bosch Master, ASE master L1
26 years MB technician