The electrolyte is pyrophoric, this means it can reignite in air.
I don't think it's true. Electrolyte in li-ion batteries is just lithium salt in an organic solvent like ethylene carbonate. It's flammable, but not pyrophoric; and it's not super flammable, flash point of EC for example is 150degC and autoignition temperature 465degC. Compare the flash and autoignition temperatures of gasoline, -43degC and 280degC respectively. The electrolyte only burns during the incident, when the cells already are hot enough to ignite the electrolyte.
The battery itself however contains oxidizer in form oxygen in the cathode (e.g. LiNiCoAlO2), and
this is the source of reignitions. This thermal runaway happens inside the battery which makes the reignition slower / benign compared to reigniting gasoline which can spontaneously combust at -43degC or higher given enough spilled gasoline i.e. good mixture.
Flammable electrolyte is not great and would be replaced if the battery industry had something better available, but it's not the root issue with battery fires, just adds to the destruction and spread of fire.
(Note how LiFePO4 cells use the same flammable electrolyte but due to their less reactive cathode chemistry and worse energy density, even if they experience thermal runaway one often sees how the electrolyte just sprays out without getting ignited, as temperatures are just a few hundred degC during the incident. (I'm not saying it doesn't happen, be careful with the LFP chemistry, too.))