Etsy inspired login/register form that ask only mail address in first step

i'm a UI designer, i study to improve my UX knoweledge and i have a doubt about a project. I have a login/register modal window that works like the Etsy login/register modal at checkout process. In the first step it contains only a field for e-mail address and a button "Proceed".

Then if the e-mail is already registered the modal say "Welcome back" and ask the user to enter the password.

If the email is not registered in the site the modal say "You are new here" and ask the customer to create an account and enter a password.

What do you think about a solution like this? Can be confusing for customers? It's an unusual pattern? Thank you for your help!