When Engineering Outruns Intelligence: A Re-evaluation of Instruction-Guided Navigation

Abstract: LLMs are often credited with recent leaps in ObjectGoal Navigation, yet the extent to which they improve planning remains unclear. We revisit this question on the HM3D-v1 validation split. First, we strip InstructNav of its Dynamic Chain-of-Navigation prompt, open-vocabulary GLEE detector and Intuition saliency map, and replace them with a simple Distance-Weighted Frontier Explorer (DWFE). This geometry-only heuristic raises Success from 58.0% to 61.1% and lifts SPL from 20.9% to 36.0% over 2 000 validation episodes, outperforming all previous training-free baselines. Second, we add a lightweight language prior (SHF); on a 200-episode subset this yields a further +2% Success and +0.9% SPL while shortening paths by five steps on average. Qualitative trajectories confirm the trend: InstructNav back-tracks and times-out, DWFE reaches the goal after a few islands, and SHF follows an almost straight route. Our results indicate that frontier geometry, not emergent LLM reasoning, drives most reported gains, and suggest that metric-aware prompts or offline semantic graphs are necessary before attributing navigation success to "LLM intelligence."