routing: mention David can also use the sphinx packet to determine EOR

routing.asciidoc

@@ -432,6 +432,7 @@ image:images/routing-onion-1.png[]
 
 We can see that Alice has created some per hop data for David.
 The short channel id is set to 0 signaling David that this payment is intended to be for him.
+Note that this example is slightly simplified, in that David can also use attributes of the onion packet format itself to be able to know when he's the final hop.
 The amount to forward is set to 3000.
 On the incoming HTLCs David should have seen that exact amount.
 Usually this amount is intended to say how many satoshis should be forwarded.