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. The are actually going to BLOCK you from even viewing reddit on your phone without using the official app.
Archive.org link in case the post is removed.
It’s not as common to push users to apps on desktop, but its a tried-and-true practice on mobile. I’m sure companies would do it if they could, but app stores and app lockin aren’t as strong on desktop as on mobile
Sorry that that wasn’t obvious, but the desktop bit was mostly a joke!
But yeah; on desktop extra applications you have to download are definitely a hard sell.