Some Reddit users have noticed that they can’t sign-in to their accounts anymore on mobile, as the option to do so has been removed for them. Reddit has made it difficult in the past for users to access the site on mobile in browsers. The company’s main intention is to get users to use the official Reddit application instead.
That’s what I was thinking - they could have broken code they were testing, but who knows nowadays ¯\(ツ)/¯