Log out and back in, and it’ll correct itself. There’s some technical reason for this “bug”. Since the forums are hosted by Discourse (the group that writes/maintains the software), WaniKani staff is probably has their hands tied on getting it to update when your level actually changes.
Me on a daily basis: “Do I immerse more Japanese, or get to more English language media I want to read/listen to/watch???”
I’m not experienced enough to say, but I feel a show like Terrance House is like a final boss in a video game. (Not to be confused with the secret boss that’s more difficult than the final boss, Classical Japanese.)
The main plus is probably furthering your ability to recognize how Japanese sounds. Initially, it’s just knowing how syllables sounds (especially the vowel portion), so that you can read it “properly”. But then once you start learning words and hearing them, you’ll start to hear specifically how each word sounds. Then eventually you are able to catch things like how あめ (candy) and あめ (rain) sound different.
I see アオハライド!