But seriously, they’ve already said it’ll be shorter than the normal raid so I bet they just don’t want to announce that ‘Worlds first’ will be 40-50 minutes after it launches.

I think it's because the community created so much toxicity around the last one, they don't want to give people an easy harassment lightning rod to whomever they announce as a winner. Community can choose their own world first. I wouldn't be surprised if WF announcements never come back. Similar to how they used to announce who won Recon but did it stealth later on.