In the minimal ΛCDM model, CMB temperature and polarization anisotropies arise from a statistically isotropic, Gaussian random field, which implies that the phases of the spherical-harmonic modes (or Fourier modes) should be independently and uniformly distributed once the power spectrum is fixed (Bond & Efstathiou 1987; Hu & White 1997). Reports of phase correlations, alignments, or other non-random structures in the low-l CMB (and in some large-scale structure statistics) therefore suggest either subtle systematics/foregrounds or genuinely non-Gaussian and phase-correlated initial conditions, requiring extra ingredients beyond the simplest inflationary ΛCDM framework that assumes random phases and nearly Gaussian primordial curvature perturbations (Copi et al. 2010; Planck Collaboration XVI 2016).