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.
This will cause search engines to deprioritize reddit threads in search results due to the ‘bounce factor’.
If it’s blocked for logged in users, why would that effect search engines?
The implication here is that if they are testing it on logged in users, then they will eventually roll it out to ALL users, whether logged in or not.