revoke through a db link

Why would someone do such a thing? Following will end up an active a user session stuck waiting "SQL*Net message from dblink".

sqlplus /nolog

connect / as sysdba


drop user a cascade;

drop user b cascade;


create user a identified by a;

grant create session to a;

grant create procedure to a;

grant create database link to a;


create user b identified by b;

grant create session to b;


connect a/a

declare 
 comm varchar2(200);
begin 
 select 'create database link b connect to b identified by b using '''||
        sys_context('userenv','db_unique_name')||'''' into comm 
   from dual;
 execute immediate comm;
end;
/


create or replace procedure p as
begin
execute immediate 'revoke execute on p from b';
end;
/


grant execute on p to b;

exec a.p@b