Hi T28D
Not sure of the brand/model engine you’re talking about there. On a bog standard injected CMI engine most or all of the fuel should be blocked by the FCU (being in ICO) and therefore not make it through to the manifold and injectors. (Although the tech data for the FCU does show that a conforming item can still let a little fuel through. It's also different on turbo models, though, because apparently the mixture mechanism is in the EDP, not FCU.)
The aim of the technique, as I understand it, is to flush cool fuel through the heat-soaked EDP (not the manifold or beyond).