As quoted from the linked post.
It looks like you’re part of one of our experiments. The logged-in mobile web experience is currently unavailable for a portion of users. To access the site you can log on via desktop, the mobile apps, or wait for the experiment to conclude.
This is separate from the API issue. This will actually BLOCK you from even viewing reddit on your phone without using the official app.
Archive.org link in case the post is removed.
It’ll take time but I think if the users who are engaged and knowledgeable enough to make this move stick to it, the riff raff that would prefer easier enough to stay in that train wreck being on the sinking ship is better than following along and ruining a good thing.