Gaussianity tests for the standardized residual fluctuations in three representative annuli. To match the adopted de Broglie wavelength, λ_dB ∼ 120 pc, each annulus is assigned a radial width of ΔR = 120 pc. For each annulus, the left panel compares the probability density distributions of the standardized residuals from the FDM and GRF realizations with the standard normal distribution, ﹩{ \mathcal N }(0,1)﹩, while the right panel shows the corresponding normal Q–Q plot. The reported statistics are the sample size n, skewness S, kurtosis K, K-S statistic D, and its associated p-value. The S–P FDM residuals are broadly consistent with Gaussian statistics within the selected annuli and exhibit good agreement with the GRF realization. See Section A.3 for further discussion.