The overwing rails were part of the Jaguar "International" design, which many would say is what the RAF should have bought in the first place, bigger donks, combat radar for sea eagle etc.
I would disagree that people were paid to put them on and take them off, as they were never part of the original specification for RAF GR1 and T2 Jaguars
They had most certainly been tested though, (causing more than one engine stall) :
