Correlations between (spectroscopic) luminosity and SLF variability parameters for the sub-samples of Milky Way, LMC, and SMC massive stars studied in this work are shown (from top to bottom). We note that the spectroscopic effective luminosity is defined as $\mathcal{L}:=T_{\mathrm{eff}}^4/g$ (Langer & Kudritzki 2014) with values taken from Bowman et al. (2020) for consistency. The uncertainties plotted are the 2σ confidence intervals from the combined methodology of a GP regression and Hamiltonian Monte Carlo with a no U-turn sampler (Bowman & Dorn-Wallenstein 2022).