I think the simple answer is that "effective altruism" is a vague term. I gave you what I thought was the best way of making it precise. Weeatquince, and Luke Muelhauser wanted to make it precise in a different way. We could have a debate about which is the more useful precisifcation, but I don't think that here is the right place for that.

On either way of making the term precise, though, EA is clearly not trying to be the whole of morality, or to give any one very specific conception of morality. It doesn't make a claim about side-constraints; it doesn't make a claim about whether doing good is supererogatory or obligatory; it doesn't make a claim about the nature of welfare. EA is broad tent, and deliberately so: very many different ethical perspectives will agree, for example, that it's important to find out which charities do the most to improve the welfare of those living in extreme poverty (as measured by QALYs etc), and then encouraging people to give to those charities. If so, then we've got an important activity that people of very many different ethical backgrounds can get behind - which is great!