What a reader sees in the Subscribe form(s) is a bit different if they are logged into a Grow account compared to if they're logged out of Grow.
Logged In To a Grow Account
When a reader is logged into Grow, they will only see a Subscribe button. They won't have to enter their email address:
Logged Out of a Grow Account
When a reader does not have a Grow account or is logged out of their Grow account, they will be prompted to add their email with the text box: