Explain why the rule looks different

docs/ghost-state.tex

@@ -67,6 +67,12 @@ from timeless propositions even when working under the later modality:
   \infer{\timeless{\prop} \and \prop \proves \later \propB}
   {\later\prop \proves \later\propB}
 \end{mathpar}
+This rule looks different from the above ones, because we still do not have that
+\begin{mathpar}
+  \inferH{later-fake-rule}{\timeless{\prop}}
+  {\later\prop \proves \prop}
+\end{mathpar}
+
 
 The following rules can be derived about except-0:
 \begin{mathpar}