Correct, if you are not sure that a certain site is a scam or not, try to register on that site using your dummy information just to test it legitimacy, because who knows it might be a Phising site, so if you are going to use your legit information, like for example your email that you have used in making a bitcoin wallet, then all of your information about your bitcoin wallet will be leak to them, and the worst thing that can happen is that, they are going to steal your bitcoin without being notice.
So, it is better to examine first before we try it, asking first will help, since there is no fee for asking, it is free.