wasn't referring to the classical meaning of utilitarianism as maximizing the happiness of everyone, but instead the meaning it seems to have taken in common parlance: any theory where decisions are made by maximizing expected total utility.

I don't think that's the common usage. Maybe the same etymology means that any difference must erode, but I think it's worth fighting. A related distinction I think is important is consequentialism vs utilitarianism. I think that the modern meaning of consequentialism is using "good" purely in an ordinal sense and purely based on consequences, but I'm not sure what Anscombe meant. Decision theory says that coherent consequentialism is equivalent to maximizing a utility function.