That's exactly what did Asseline in Habsheim when he realized thrust was not coming.
And it helped, did it?
It's possible to 'rich cut' a carb-fed
piston engine by being aggressive on the throttle at a low power setting, on something with an accelerator pump... Maybe people get confused by this and expect jet engines to exhibit the same behaviour.
The only way I know to 'reset' the Trent engine is to momentarily put the fuel control switch into cutoff and hope that it will accelerate up again; even the manual says it could take a loooonnng time. Not a technique I'd apply at 700'.
