diff --git a/docs/formats/core-data-regions.md b/docs/formats/core-data-regions.md
index 5819596..bcc54cf 100644
--- a/docs/formats/core-data-regions.md
+++ b/docs/formats/core-data-regions.md
@@ -3469,6 +3469,28 @@ intra-span offset. Distinguishing them needs either the engine's class loader
 (readable now, in the same overlay's `.text`) or a class whose animation is known
 from outside, and neither has been done.
 
-So `moby_anim` is **not** unblocked. What the attempt establishes is that the
-search has a specific place to look, a specific field count to classify, and a
-specific reason the obvious discriminator fails -- which is more than it had.
+### And the discriminator fails for a sharper reason than "they are small"
+
+Two tests, both cheap:
+
+**No header `u32` equals the span's own table offset** on any of the 187 classes.
+So the varying fields are not self-relative pointers to the part table.
+
+**The largest value in any header `u32` is 3,332,678,933.** Some of these fields
+are not offsets at all -- at `+0x0c` the value is 16,711,748 across classes, which
+is packed data or an identifier, not a displacement.
+
+So the header's varying fields are a **mixture**: some hold in-span offsets
+(`+0x10..+0x1c` run 192 to 10,800, comfortably inside the spans) and some hold
+packed values far too large to be offsets. There is no single "the field that
+points to the animation" to find, because not all of them point anywhere.
+
+That is a real narrowing even though it is a negative: **if per-class animation
+data exists on the disc, it is inside the class span**, not at a separate pointer
+target. The search therefore stops looking for a pointer and starts looking for a
+region *within* the span that the geometry parser does not already account for --
+which is a bounded question with the parser as its control.
+
+So `moby_anim` is still **not** unblocked, but the question is now bounded rather
+than open-ended, and the next step is to subtract the parsed geometry from the
+span and look at what remains.