Suppose we have an escalation running and disable its action. The next time this escalation is processed by the escalator, the server will send out an email with the default message, prefixed by "NOTE: Escalation cancelled: ...", and run all other commands specified for this step. Only then will it remove the escalation.
The same thing happens, for instance, if you disable an item, a trigger or a host for an action started by a trigger going into PROBLEM state.
A related problem is that, if escalation is cancelled, then a message about it will only be received if sending out emails is configured for this escalation step. It might be reasonable to send this message to the same recepients as for recovery message. Otherwise, there will not be a recovery message either, so nobody will know that the escalation was cancelled.