This paper argues that addressing the overconfidence problem of deep learning-based object detection models on Out-of-Distribution (OoD) inputs requires a comprehensive rethinking of the development lifecycle, beyond algorithmic improvements such as improving the existing scoring function and adjusting test-time thresholds. We highlight the errors (up to 13% contamination) of existing OoD detection evaluation benchmarks and propose a novel training-time mitigation paradigm that fine-tunes the detector using a semantically similar OoD dataset, without relying on external OoD detectors. This approach reduces hallucination errors by 91% in the BDD-100K environment for the YOLO model, and demonstrates generalizability to various detection methods, including YOLO, Faster R-CNN, and RT-DETR, as well as to small-shot adaptation.