As of Ant 1.9.1, you can use 'if' and 'unless' attributes on any task or element in a target. I stopped using Ant a long time ago, but this was a pleasant discovery when I had to pick up an old Ant based project recently.
I agree, that is what I meant: there were people who installed Contrib to have <if> element, but in reality you did not need that you could just use Ant's built-in features like you said. In my opinion installing Contrib to use <if> was a demonstration of not having understood how Ant works.
https://ant.apache.org/manual/ifunless.html