The Java RMI specification (latest published version here : https://docs.oracle.com/en/java/javase/24/docs/specs/rmi/index.html) has several mentions of applet use cases

under System Goals :

    Support callbacks from servers to applets

Handing of properties in applet cases

 Note that properties are typically restricted from being set from applets.

There are numerous mentions in the sections on Wire Protocol

Given that the intention is to remove the Applet API (see JEP 504) and that applets are already unsupported anyway, this specification should be updated.