Add clarification on reduced filtering of subscriptions

Author: darrellwarde

modules/ROOT/pages/security/subscriptions-authorization.adoc

@@ -3,7 +3,7 @@
 = Subscriptions authorization
 
 Subscriptions require their own authorization rules, which are configured with the `@subscriptionsAuthorization` directive.
-These rules are different to authorization rules for queries and mutations because they use filtering rules available for subscriptions events.
+These rules are different to authorization rules for queries and mutations because they use filtering rules available for subscriptions events. These filtering rules can only be used to filter against the properties of the nodes impacted by the events - they cannot be used to arbitarily filter across related nodes as in the schema generated by the Neo4j GraphQL Library normally.
 
 All subscriptions authorization rules have an implied requirement for authentication, given that the rules are normally evaluated against values in the JWT payload.