> With Android being the concrete pillar of stable OSes that it is, I would blame them for building a phone that can explode because of a software flaw.

Obviously they didn't build a phone that can blow up on purpose, and you don't actually have to have a real chance of it happening for other models for your legal department to tell you to cover your ass really, really well. It's not like these batteries haven't exploded in other contexts as well. Li-Ion batteries have been known to explode for a long time now. The problem with Samsung's phones was a defect that caused it to be far more likely. Also, the difference between software and hardware is much more fuzzy these days when talking about firmware. Some chips (what you might consider hardware) in the phone have their own little operating systems embedded and running in them.