No. FP is a test where the fluid in a dish is heated under a flame. When the flame ignites the vapors the temp the dish/fluid was at is called the flash point(open cup).
" LEL and vapor build-up is more approrpriate."
Those considerations are inherently contained in the flash point test.
In another life, I ran at least 15 FPs a day, both OC and CC. Today, I work in the petroleum liquids handling industry.
The reason I say FP is non sequitor is that the ambient temperature relative to the FP temp is simply an indication of what happens at the ignition source. In the right concentration, vapors don’t need to be at FP-temp to ignite - if there is an ignition source (LEL).
What I speculate happened here is that vapors from the loading event moved to an ingnition source. The flame followed the vapor trail back to the loading point and “boom”.
Lots of specific things could have been the cause, including improper loading operations. Only extensive forensics will pin-point the cause.