An idea is discussed in Colin Mclarty's https://webusers.imj-prg.fr/~leila.schneps/grothendieckcircle/Mathbiographies/mclarty1.pdf which could be where your paraphrase of Grothendieck's method originated. That source does give quite a lot of background for this so may be of use to you.

An idea is discussed in Colin Mclarty's paper "The Rising Sea: Grothendieck on simplicity and generality I" which could be where your paraphrase of Grothendieck's method originated. That source does give quite a lot of background for this so may be of use to you.