This is the same Beeb that calls terrorists "militants" and illegal immigrants "migrants". They're so far to the left they can only walk in circles.
There is that, but the BBC is also being cautious, albeit needlessly in this case.
'Hit and run' has connotations of a criminal offence, which this almost certainly was.
But the BBC has no source for the detail of what happened.
The police, quite properly, will only release a limited amount of information, not least because that's all they know at this stage.
You could say as a simple matter of description the cyclist was hit and the driver 'ran' off, but to be absolutely cautiously on the safe side, saying that is what you suspect happened is safer.
Bear in mind the BBC has been sued a couple of times now for what we could call over enthusiastic reporting of suspected crime.