I do love it when some old fart makes statements like this, seemingly believing that AVTUR is somehow more high performance than AVGAS.
An Air Force needs as higher performance fuels as are available
As already touched upon, the alleged "higher performance fuels" the RAF use are kerosene-based, the stuff that can be used in lamps and heaters!
As an aside, the production and trial usage of synthetic kerosene fuels is old news, with Germany (among others) already funding increased development of sites for producing such fuels