Apple's design is slipping
Watching Louis Rosmann's videos of Apple's board design, it doesn't surprise me. The most obvious example is where there used to be a ground line on the macbook display ribbons, between the high voltage and signal wires... but they did away with that line, meaning that the signal traces were being melted by the close proximity to the higher voltage trace on occasions.
I can't work out why Apple, of all companies, hasn't corrected design elements like this after being called out by the likes of Rossman.
There's a chance that this fire wasn't a fault of the battery itself, but the design of the device. Grab the popcorn, this is going to be a good one.