[AaronLancs]

I have a feeling that the final version of the titles weren’t ready yet (they had the “On TV, On Radio, Online” slogan), so they used those for the first few days after the 21st April rebrand. By 2019 a few other regions were using that altered music before the standardisation in July that year.

The "On TV, On Radio, Online" slogan was / is and will always be uniquely BBC London's territory. The audio tag for me kind of signified the BBC English Regions to have a unique audio 'ident' that is akin to what BBC Reporting Scotland has to this day.

Here is the BBC South Today title post BBC Newsroom South East split to demonstrate the audio signifier.
youtu.be 

P.S. Apologies to the mods if it is from a blacklisted YouTube account but with there being no proper presentation sites that have this sort of video content easily linkable to post on this forum / message board I have to use them, sorry. Tried everything to get something from TV Whirl no less but got nowhere (after a good 15 minutes of trying).