My understanding is that the self-effacing utilitarian is not strictly an ‘ex-utilitarian’, in that they are still using the same types of rightness criteria as a utilitarian (at least with respect to world-states). Although they may try to deceive themselves into actually believing another theory, since this would better achieve their rightness criterion, that is not the same as abandoning utilitarianism on the basis that it was somehow refuted by certain events. In other words, as you say, they’re switching theories “on consequentialist grounds”. Hence they’re still a consequentialist in the sense that is philosophically important here.
My understanding is that the self-effacing utilitarian is not strictly an ‘ex-utilitarian’, in that they are still using the same types of rightness criteria as a utilitarian (at least with respect to world-states). Although they may try to deceive themselves into actually believing another theory, since this would better achieve their rightness criterion, that is not the same as abandoning utilitarianism on the basis that it was somehow refuted by certain events. In other words, as you say, they’re switching theories “on consequentialist grounds”. Hence they’re still a consequentialist in the sense that is philosophically important here.