What if someone creates a browser extension to change now Facebook looks? How is that any different from these apps? Why is it Facebook’s business what I do wit

What if someone creates a browser extension to change now Facebook looks? How is that any different from these apps? Why is it Facebook’s business what I do with their HTTP data that they send to me? For example social book post manager (https://chrome.google.com/webstore/detail/social-book-post-manager/ljfidlkcmdmmibngdfikhffffdmphjae https://chrome.google.com/webstore/detail/social-book-post-m...) lets you bulk delete your Facebook history, or at least it used to before Facebook’s repeated updates broke it. Isn’t that a “third party app” basically?