The Loess Plateau hosts the thickest aeolian loess deposits in the world, forming an exceptionally deep vadose zone. Under this unique geological setting, whether precipitation can penetrate thick loess profiles to recharge groundwater has long been a central scientific question in hydrogeology. Based on a systematic review of the regional hydrogeological background, this study synthesizes and evaluates two contrasting perspectives and their supporting evidence. One perspective suggests that, under the combined influence of piston flow and preferential flow, precipitation can migrate downward either gradually or rapidly through preferential pathways, thereby contributing to long-term or event-based groundwater recharge. The opposing view, drawing on evidence from dried soil layers, soil water deficits, loess–paleosol stratification, and the water-blocking effect of unsaturated fractures, argues that infiltration depth is limited, with most precipitation participating only in shallow soil water cycling and failing to penetrate the thick vadose zone; deep groundwater may instead largely consist of “paleo-groundwater” formed under past climatic conditions. Further analysis indicates that discrepancies between these views primarily arise from differences in research scale, observational methods, and geomorphic settings. Small-scale or event-based studies tend to capture rapid processes such as preferential flow, whereas regional-scale and long-term observations more often reflect slow or restricted infiltration. In addition, pronounced hydrological differences among geomorphic units (tablelands, slopes, and gullies) lead to strong spatial heterogeneity in groundwater recharge. Integrating available evidence, this study concludes that groundwater recharge in thick loess regions is not governed by a single mechanism but is instead a complex and heterogeneous process. The capacity of precipitation to directly penetrate the deep vadose zone via diffuse infiltration and form regional groundwater recharge is likely limited. Future research should emphasize long-term monitoring of deep vadose zones, the integrated use of multiple tracers, and multi-scale analyses to better constrain the coupling between precipitation infiltration and groundwater recharge.