Linguistic research consistently shows that existential sentences are subject to the definiteness effect, which restricts definite noun phrases from functioning as pivots.
The claim refers to the well-documented syntactic 'definiteness effect' in existential sentences, where certain noun phrases (definite ones) are infelicitous or barred from appearing as pivots. Papers [0], [3], and [11] all explicitly discuss existential constructions and the constraints regarding definiteness and pivots. No papers refute this claim. Thus, the verdict is SUPPORTED.