It has nothing to do with verification.
They are simply reporting what sources have said:
Houthis 'take control' of Perim Island - government source published at 09:00
Houthi rebels have "taken control" of Perim Island in the Bab al-Mandab Strait, according to a source. Earlier, we were reporting that the group had reached the key island.
The AFP news agency also says Houthis have "taken over" Perim Island, also referred to as Mayyun, according to eyewitnesses and a local government official.
"Boats carrying armed Houthi fighters reached Mayyun Island after government forces withdrew from it yesterday," the official tells AFP.
My point about verification is simply that if the BBC had independently verified it’s true then they wouldn’t use the quote in the headline. They’d just say taken control without quote marks, because it wouldn’t be a quote.