I think I can shed at least a little light on this situation. My Primary driver is a 2019 Bolt Premier, which is having by far the most fires. After doing much research it appears to be Bolt batteries manufactured in Ochang, Korea. All 2017, 2018 and half of 2019 Bolts have batteries from Korea. Luckily I have confirmed that my 2019 Bolt has the batteries made in Holland, Michigan USA. All 2020 and 2021 Bolts also have batteries made in Michigan. I figured this out by decoding the numbers on a sticker located under my bolt. Also, I was not included in the July Bolt recall.
Apparently, GM has identified two simultaneous battery defects in some batteries made in Korea, especially the Korean battery 2019's.
The 2015 and 2016 Spark EV batteries were made in Holland, Michigan also. Good news!
I have found no Spark EV or Bolts with American batteries catching fire. Which is a good thing since these are the cars we keep in the garage.
12 Bolt fires with Korean batteries
0 Bolt/Spark fires with Michigan batteries.
For the record, we love both cars.
2016 Spark EV LT2 DCFC (USA battery)
2019 Bolt Premier DCFC (USA battery)
2005 Honda Insight 63mpg (Lifetime)