It seems based on questionnaires sent out about projects, and they've found some correlation between "uniqueness of a project" (unclearly defined) and cost over

It seems based on questionnaires sent out about projects, and they've found some correlation between "uniqueness of a project" (unclearly defined) and cost overruns. Because "uniqueness" is unmeasurable, they can provide various examples in prose where both arguments and counterarguments for uniqueness seem reasonable. So this isn't really science. But the overall argument; that uniqueness bias (in so far it exists) causes managers to be less critical, seems reasonable.