It doesn't seem like they know who still works there vs not (or in the process of resigning). First they have to fix this situation before they even know what roles they need to hire for.
They wouldn't need a careers page to know who to hire, generally careers pages are for applicants.
So, given the current environment at Twitter, the parent post you responded to seems to have hit the nail on the head. Give things time and it will get back to normal, and we can expect new opportunities to be posted on some sort of careers page for Twitter.
People are really looking hard for reasons to be negative about Twitter and Musk. This careers page isn't one of them...
It's all speculation based on nothing of substance. That's why I asked GP to expand on his thought process.