diff --git a/src/picture.c b/src/picture.c
index 013371a..785b4a4 100644
--- a/src/picture.c
+++ b/src/picture.c
@@ -378,6 +378,15 @@ VAStatus RequestBeginPicture(VADriverContextP context, VAContextID context_id,
 	 * first. The new slot is bound and its V4L2 index + mmap pointers
 	 * are mirrored into surface_object->destination_* so the existing
 	 * QBUF/DQBUF/EXPBUF code paths see no behavioral change.
+	 *
+	 * AV1 Phase 3 finding: LIBVA_SKIP_REBIND=1 experiment (do NOT
+	 * unbind on rebind) did not improve PASS count for the av1_larger
+	 * film_grain stress vector — proving the iter2 Fix 3 release is
+	 * NOT the source of the inter-frame divergence. The issue is
+	 * deeper in ffmpeg-vaapi's AV1 hwaccel: per byte-equal OUTPUT
+	 * comparison with the patched-ffmpeg-v4l2request reference run
+	 * (LD_LIBRARY_PATH override on a debug libavcodec.so), 7/7 first
+	 * EndPicture submissions are byte-identical, libva has 2 EXTRA.
 	 */
 	if (surface_object->current_slot != NULL)
 		surface_unbind_slot(driver_data, surface_object);