GDPR?
I presume the BBC's get-out is that registration is not necessarily "personally identifiable", given that you can (and should) use any throwaway e-mail address.
However, it does not really address the issue that it's quite happy to shovel this material out over the airwaves without knowing who's listening, so quite why, if you have the temerity to listen via the Internet, you have to accept telemetry via the Internet is not clear. And bloody iPlayer trailers.
Cough, get_iplayer, cough.