This website contains age-restricted materials including nudity and explicit depictions of sexual activity.
By entering, you affirm that you are at least 18 years of age or the age of majority in the jurisdiction you are accessing the website from and you consent to viewing sexually explicit content.
I got the same error.
Edit: I just read the article you linked. Why do we need to sign in with Google at all? Granting an unknown publisher access to my Google account, which knows pretty much everything about me, including financial information, seems unwise.
They don’t have access to that info. Just name and email for subscriptions.