If you chose the email option instead of “sign in with Google”, the server will probably use that email address to send you a login link. This is pretty standard for any web service, even blogs, where users can create accounts.
Given that - presumably - you are going to be asked for content such as voice recordings to create the clone this is a valid concern.
I only see a title, a sign up link, and some celebrity photos.
It's a site where you can create voice clones of someone and talk to them.
You can tap on the celebrities to chat with them as a test