<p>The reliability of aeroengine main-shaft bearings is critical for airworthiness, yet they remain susceptible to Rolling Contact Fatigue (RCF). Despite extensive research, an inherent contradiction persists regarding whether microstructural evolution involving features like White Etching Areas, act as precursors to or consequences of crack nucleation. Furthermore, current computational frameworks critically fail to fully couple chemo-mechanical diffusion, phase transformation kinetics, and explicit crack nucleation under realistic contact kinematics. To resolve these limitations, this review critically examines subsurface crack initiation and microstructural evolution specifically in aviation bearing steels (e.g., M50). We evaluate the methodological trade-offs among Continuum Damage Mechanics, Crystal Plasticity FEM, Peridynamics, and emerging physics-informed machine learning approaches. The available evidence supports a conditional interpretation: microstructural degradation may precede crack nucleation in inclusion-centered damage, whereas crack-assisted WEA formation may occur under other conditions. Stress-assisted carbon redistribution, phase transformation, and hydrogen-enhanced localized degradation are identified as key contributors to these processes. Based on this synthesis, we propose a multiscale computational roadmap that couples microstructural evolution and diffusion with non-local fracture modeling. This framework defines the principal modeling interfaces and material-specific validation requirements for predicting the transition from subsurface defects to spalling in M50 and M50NiL bearing steels.</p>