Update comment about Weaver slot assertion

Explain more clearly why this assertion is important.

Test: comment-only change
Bug: 356562932
Change-Id: I0ef2862fb6fbb062520c98935d347f1445a7dfae
diff --git a/weaver/vts/VtsHalWeaverTargetTest.cpp b/weaver/vts/VtsHalWeaverTargetTest.cpp
index 40e9558..8952dfc 100644
--- a/weaver/vts/VtsHalWeaverTargetTest.cpp
+++ b/weaver/vts/VtsHalWeaverTargetTest.cpp
@@ -221,7 +221,10 @@
         }
     }
     // Starting in Android 14, the system will always use at least one Weaver slot if Weaver is
-    // supported at all.  Make sure we saw at least one.
+    // supported at all.  This is true even if an LSKF hasn't been set yet, since Weaver is used to
+    // protect the initial binding of each user's synthetic password to ensure that binding can be
+    // securely deleted if an LSKF is set later.  Make sure we saw at least one slot, as otherwise
+    // the Weaver implementation must have a bug that makes it not fully usable by Android.
     ASSERT_FALSE(used_slots.empty())
             << "Could not determine which Weaver slots are in use by the system";