It's not just that people affected by this vulnerability are being protected by its disclosure (though there are reasons why that might be the case) it's that in the future vendors will take deadlines from P0 far more seriously when they realise that their reputation is on the line if they fail to patch in time.
If you let vendors get away with "we know that this is being actively exploited, but we haven't been able to come up with a timely fix, so please don't tell our customers how screwed they are", then that becomes the standard line and you need to keep letting deadlines slip. Or you don't let them slip and you end up with this sort of situation.