The rule underneath all three
Every cumulated sp-carbon and every spiro atom twists the next plane by 90°. Count these orthogonalising centres:
ODD centres → ⟂ endschiral · no σ → OPTICAL
EVEN centres → ‖ endsσ present → GEOMETRICAL
Surface count: cumulene even C=C and spiro even rings → optical; odd → geometrical.
Biphenyls reach the same ⟂ geometry through a rotation barrier (atropisomerism), not a structural centre — so the test is simply: twisted and no σ.