Depending on the region where they were sold, Samsung Galaxy S20 could use either Snapdragon 865 or Exynos 990 CPUs.
The Mozilla messages fail to mention this information that is essential for any CPU bug, which CPU model was used in the phones with crashes.
It is more likely that the bug is present in the Samsung Exynos 990 CPUs and not in Snapdragon, because Cortex-A77 was used much more widely, so it is improbable for such a bug to not also be noticed elsewhere.