One could argue that if you experienced romantic attraction at some point in your life you are technically not aromantic. But the important point is that what counts is how one is actually feeling an not how they can be technically defined. If most of ones life experiences is similar to that of aromantic people of course one can relate much more with aromatic people than with romantic people. So telling them they are alloromantic just doesn't make sense, because they share much more experiences with aromantic people than with alloromantic people. If you feel still different from aromatic people due to the experiences you had that's exactly what the greyromantic label is for.
