I think the claim that PhDs and postdocs are fungible is what enables credit to be concentrated to the PI.
In top places though, it’s often the case that trainees have an idea, get shut down by PI, trainee demonstrates project can work, then PI changes mind.
Also in science, the usual progress of a project is often PI has an idea, trainees explores the idea, finds an even better idea, PI says great now write the paper.
But I agree with you in the sense that PIs act as the “quality control” or “selection process” whereby ideas get culled and refined. And their scientific taste is non fungible.
In top places though, it’s often the case that trainees have an idea, get shut down by PI, trainee demonstrates project can work, then PI changes mind.
Also in science, the usual progress of a project is often PI has an idea, trainees explores the idea, finds an even better idea, PI says great now write the paper.
But I agree with you in the sense that PIs act as the “quality control” or “selection process” whereby ideas get culled and refined. And their scientific taste is non fungible.