OP has a CX ticket. Not EK and not LH. Thus, what some other carrier might do on some other ticket at some other time is irrelevant.

In this case, if OP is simply willing to forgo the value of the ticket, he should do nothing. CX will not and cannot pursue him for the cancellation fee, because it is inapplicable. On the other hand, if CX cancels or there is a significant delay, OP will become eligible for a full refund of the ticket to his original form of payment.

Thus, notifying CX is at best of no advantage to OP and at worst, may cost him a refund.

Don't worry about CX. It has calculated the percentage of passengers likely to no show and will overbook to deal with that (should loads even come close to requiring that).