Planets orbiting on a nearly common plane is a fundamental descriptive characteristic of our solar system derived from the conservation of angular momentum during protoplanetary disk formation.
The claim that planets lie on the same plane due to protoplanetary disk formation is a standard astrophysical fact of solar system formation stemming from the conservation of angular momentum in collapsing nebulae. It does not require specific citation of a disputed study, though background papers on protoplanetary disks and solar nebula history align with the physical principles.