[cityprod]

Because they are the most watched, therefore when you say BBC News, most people think about the 6 & the 10 on BBC1, rather than anything else.  Hence, the sub brands actually help identify the source better.  I heard a story and it was only on the World Service news bulletins, nowhere else, so I would say I heard it on World Service News.  Where as saying I heard it on BBC News, doesn't tell you it was on the World Service only, not anywhere else.  Hence, the brand is diluted, by spreading it thinner over more sources.

Once again, this just isn't want brand dilution is - quite the opposite.

Also I really think most people would say 'I heard it on the BBC' - this specific academic-level referencing to specific news bulletins is not a particularly common occurrence. Even if you were pointing people in the direction of a particular programme, why would you ever point people towards BBC News bulletins on the BBC World Service - they are surface-level summaries. If people were interested in a particular story, you'd point them towards Newshour or whatever.

Plus the reason why everything is called BBC News is because it's a single source across multiple platforms. If a story is being covered on BBC News radio, it's also being covered on BBC News online/app and probably on BBC News TV as well. This is literally the whole point - BBC News is a single news organisation producing BBC News content across three mediums under the same BBC News brand. When it's on at Six, it's the BBC News at Six; when it's on their channel, it's the BBC News channel; when it's on their website, it's the BBC News website; and so on.

Except I ONLY heard this on the World Service bulletins, it WASN'T on the BBC website, I didn't see it or hear it anywhere else.  It's not a "single source", it's different products on different stations.  Something gets diluted when it gets watered down.  Tell me how you are not watering down the whole BBC News brand by requiring it to carry many different products that all need to do different things for different audiences.