And if the UK rejects an update, that update cannot be released in any other nation and the public would not be informed of the decision.
So,… say, I find a major bug in a widely used software and inform the vendor. Said vendor informs the UK bodies and they reject the update and it is bound by the decision to stay silent and don’t patch it. What stops me now to go full public disclosure of the matter? From my perspective I told them the big, I might even have confirmation, that it’s worked on and then… silence. The only way to get this patched in a timely manner would be massive public pressure.
First - if I’m not from the UK, thats very unlikely. At least because the UK wants it to happen and not for other reasons.
Second - the moment the information is out, it’s too late. Their zero day is burned.
Third - the police needs to know where to knock. If I publish the information in a way that can be associated with my identity and I’m the one that alerted the vendor, sure. But even if I’m a completely random person that immediately goes full disclosure - doing so may in a way that identifies me might hurt me anyways, depending on my jurisdiction. So for individuals it might be the smarter play to make it less traceable.
Fourth - imagine Google’s Project Zero or another “huge player” finds the Bug and alerts the vendor. Google e.g. has a policy to fully disclose the bug, if there’s no fix within a specified time-frame. This might be extended for reasons, but only of there’s a good reason. If the vendor cannot say why they don’t patch, well that’s none of these reasons.