This is different though - Facebook wasn’t rebranded to Meta, Facebook is still the official name for Meta’s product. Meanwhile most of Twitter’s logos and other branding have been replaced.
And yet the vast majority of humanity, who do not use Twitter and who, at best, merely know about it in passing, are not in a position to observe this rebrand and would be confused by even calling it "Twitter/X", as though that's some sort of new product under the Twitter brand. Calling it Twitter just reduces confusion.