Clarify that per-files that reference OWNERS files do not support annotations

Signed-off-by: Edwin Kempin <ekempin@google.com>
Change-Id: I5f2365eab29e3e09078ed17ee8bbeb3fc41bae09

resources/Documentation/backend-find-owners.md

diff --git a/resources/Documentation/backend-find-owners.md b/resources/Documentation/backend-find-owners.md
index 846e8d9..1ea48ab 100644
--- a/resources/Documentation/backend-find-owners.md
+++ b/resources/Documentation/backend-find-owners.md
@@ -371,10 +371,12 @@
 annotation, this annotation applies to all these users. E.g. if an annotation is
 set for the all users wildcard (aka `*`) it applies to all users.
 
-**NOTE:** Only [email lines](#userEmails) and [per-file lines](#perFile) support
-annotations, for other lines (e.g. [file lines](#fileKeyword) and [include
-lines](#includeKeyword)) annotations are interpreted as [comments](#comments)
-and are silently ignored.
+**NOTE:** Only [email lines](#userEmails) and [per-file lines](#perFile) that
+assign code ownership directly to users support annotations, for other lines
+(e.g.  [file lines](#fileKeyword), [include lines](#includeKeyword) and
+[per-file lines](#perFile) that reference other `OWNERS` files via the
+[file](#fileKeyword) keyword) annotations are interpreted as
+[comments](#comments) and are silently ignored.
 
 ### <a id="comments">Comments