Post from Electrics bikes by Doc Wui: Grin Techbology's take on ebike fires and UL testing, March 13, 2024,
The first part is the history , but you can skip to around the 30 minute mark. The takeaway is they could not get a modern battery with brand name cells to catch on fire, He believes it's low quality cells, not user abuse, to be the root cause of spontaneous fires. .UL testing won't catch low quality,
This very informative video shows how and why ebike batteries can fail.