When to use timeouts and monitors in Erlang?

The Learn You Some Erlang book has the below code. Why does the book sometimes use just timeouts and sometimes use both monitors and timeouts? In the below what is the need for the monitor since the timeout will effectively detect if the process is down?

%% Synchronous call
order_cat(Pid, Name, Color, Description) ->
    Ref = erlang:monitor(process, Pid),
    Pid ! {self(), Ref, {order, Name, Color, Description}},
    receive
        {Ref, Cat} ->
            erlang:demonitor(Ref, [flush]),
            Cat;
        {'DOWN', Ref, process, Pid, Reason} ->
            erlang:error(Reason)
    after 5000 ->
        erlang:error(timeout)
    end.

Also compare the following where add_event doesn't use a monitor but subscribe does

subscribe(Pid) ->
    Ref = erlang:monitor(process, whereis(?MODULE)),
    ?MODULE ! {self(), Ref, {subscribe, Pid}},
    receive
        {Ref, ok} ->
            {ok, Ref};
        {'DOWN', Ref, process, _Pid, Reason} ->
            {error, Reason}
    after 5000 ->
        {error, timeout}
    end.

add_event(Name, Description, TimeOut) ->
    Ref = make_ref(),
    ?MODULE ! {self(), Ref, {add, Name, Description, TimeOut}},
    receive
        {Ref, Msg} -> Msg
    after 5000 ->
        {error, timeout}
    end.