It seems this may have only affected the X on iOS App. [1] That greatly expands the range of possible causes. It also makes this quite odd in another way as well, because it suggests this was not a server side change.
Why wouldn't phishing fall under trust and safety? Perhaps not primarily - but it's definitely a trust and safety event.
They wouldn't "have been the ones to flag something like this down". It should've been caught long prior; the code shouldn't have been written, it shouldn't have survived code review, and it should've failed automated tests.
It's a trust and safety incident now, but it never should have been.
The trust and safety team was only responsible for censoring wrongthink