The evolution of mobile communications within 3GPP is now entering a pivotal phase with Release 20 (Rel-20), which strengthens 5G Advanced while preparing the foundation for 6G. Within this framework, resilience has become a key priority, particularly for Non-Terrestrial Networks (NTN). The recently approved 3GPP Study Item “Study on GNSS Resilient NR-NTN Operation” addresses a critical dependency of current NTN systems on GNSS for uplink timing and frequency pre-compensation. In scenarios where GNSS is unavailable, degraded, or compromised, large timing and Doppler uncertainties may arise, directly impacting initial access and connected-mode performance. Following this 3GPP case study over the past months, this work evaluates uplink timing and frequency errors under GNSS-unavailable conditions across multiple uncertainty models and satellite geometries.