You’ve got the understand that the BBC is a big, international, serious news organisation. They can’t just be broadcasting news because some guy on Twitter said X. Stuff needs to be verified and checked.
It’s why the big news organisations are often later to the party than, for example, a football forum.
Say a false Chinese whisper goes round that Putin has dropped a nuke. Some guy in Ukraine Tweets it and it gets picked up on here - well that‘s one thing. BBC News reporting it, only having to then retract it is a whole other thing.