Sounds like the product team had difficulty coming up with a name. You probably don't want to name it Twitter Premium if there's nothing exactly premium there except for an undo button and color choices, and Premium or Enhanced imply that their base product isn't sufficient. If you remove Twitter <adjective> from the consideration, really all you can do is come up with a name that's somewhat disjointed but related to the product.
I was thinking of Twitter as a social/comment/news webapp company using the word "plus" to market a new product in a space where a cash-rich competitor with a decade-old product with broadly similar functionality already uses the word "plus" as the entire name of their own entry in the category.
An analog might be game publisher King (maker of Candy Crush Saga) initiating legal proceedings against makers of other games that used the word "Saga" or "Candy", e.g. "Banner Saga"[1], even though those are obviously not reasonable claims -- and I think they lost? Regardless, they're still able to try, and it exerted pressure.
So, imagine you're sitting in a board room at Twitter, naming your new social web app product, and someone says, "How about 'Twitter+'?", and you know there's Disney+, and Apple TV+, and Google+ all already out there, and you say, "nah... that sounds like a headache we can do without." But maybe not, hence why I noted I was merely wondering.
