IMO it would be fine to say "we were tracking you but when you followed the link we deleted those cookies and won't now set them". "Reject all", or default off ("no cookies are set, cock here to enable the committee types you wish") is better.
What's far worse is the admission that they still use ad networks even when those networks are clearly breaking the law (ie they offer no settings to disable tracking). Indeed BBC should be going further and not allowing advertisers on their network to drop cookies if a user has disabled first-party cookies. Instead they say "go to these networks and disable it yourself", good luck with that!
This from an org funded in [minor] part by taxation and whose rausin d'etre is supposed to be serving the public interest.
It's sneaky, immoral, unethical and illegal. It also works.