I'm not at all sure that we have a real alternative to "signaling that you need to compare charities".

It's still about comparing but by the rewrite it's a bit more implicit comparison not an explicit one. the "compare" step happens in someone's head ("thinking about where the money might be best spent"), not by being told "you should compare the things you donate to". It may seem like a subtle change; but I think it makes a difference.

makes some people withdraw

As far as I know - EA's don't want this to happen at all... Ineffective is still something.