Objective: The goal was to investigate the relationship between methodological adherence and clinical outcomes in Progressive Resistance Training (PRT) for Parkinson's Disease (PD), specifically identifying why findings of "superiority" over active controls remain inconsistent. Methods: This umbrella review utilized a multi-stage process to identify a sample of the primary literature for methodological analysis. An initial search identified 38 systematic reviews published within the specified timeframe. From the reference lists of these reviews, a subset of 34 primary clinical studies was purposefully selected. Inclusion was prioritized for studies providing comprehensive methodological data on PRT protocols and standardized clinical outcomes. Interventions were evaluated using a three-tiered framework: (1) training protocol with specifications of Frequency, Intensity, Time, Type, Volume, and Progression (FITT-VP) (General Exercise), (2) FITT-VP integrated with the American College of Sports Medicine (ACSM) Supplementary Guidelines (Integrated Guidelines), and (3) principles of progression (mechanistic growth). Studies were categorized by control type (active (e.g., aerobic or balance), n = 26; passive (e.g., standard care or no exercise), n = 8). Results: In trials that compared PRT with an active control group, PRT achieved clinical superiority in 57% (n = 15) of trials and 46% (n = 12) when focusing on trials with an effect on specific functional or balance outcomes. Among these successful interventions, 75% maintained high adherence (≥70%) to the Integrated Guidelines, and 58% maintained high adherence to the principles of progression. In the 53% (n = 14) of studies where PRT was found non-superior (equivalent or inferior in functional or balance outcomes) to an active control, 0% met the high adherence threshold for progression. While general FITT-VP compliance remained high (78%), the failure to implement systematic load, specificity, and variation served as a definitive barrier to competitive superiority. In the 100% of studies where PRT outperformed passive controls, high progression was present in 57% of cases. This may suggest that while a baseline resistance stimulus outperforms inactivity, it is fundamentally insufficient to outperform other active clinical therapies. Conclusions: This umbrella review indicates that adherence to the principles of progression may be an important factor influencing the clinical outcomes of PRT in individuals with PD. The variability observed in the current literature suggests that inconsistent application of established exercise frameworks-rather than the failure of the modality itself-could be a contributing element to the reported "inconclusiveness." To potentially enhance functional outcomes and the comparative effectiveness of PRT, future research should consider prioritizing structured adherence to FITT-VP, Integrated Guidelines, and progression-based frameworks. Establishing a 70% adherence threshold is proposed as a potential benchmark to improve protocol consistency and support rehabilitation efficacy in this population.