Similar doubts were investigated by the USAF re the fuel dumping from an F-111 and would the afterburners light up the dumping fuel. Test revealed that the flame front of the dumping and burning fuel never reached closer that a few feet from the dumping exit between the engine/afterburner exhaust nozzles. Hence the F-111's spectacular dump and burns.
...By the RAAF's F-111. I've not heard of any efforts by the USAF, to do so, and I thought (and am happy to be corrected) that it wasan Aussie innovation.