Critical nematic correlations throughout the superconducting doping range in Bi2−zPbzSr2−yLayCuO6+x

points to unidirectional charge modulations. By computing new critical exponents at free surfaces including that of the pair connectivity correlation function, we show that these locally 1D charge modulations are actually a bulk effect resulting from classical 3D criticality of the random field Ising model throughout the entire superconducting doping range.