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.
TBH this is nothing new. They already randomly restrict you from viewing any type of nsfw content on the mobile browser version. It prompts you to download the app with no option to close the prompt.
Oh yeah, i noticed and it pissed me off so much. Thank god people made stuff like viewditt, where you just need to replace parts of the URL to at least see the content. Regardless terrible user experience that gets worse each year.