Except for the fact that was more than likely a slip of the tongue, as has already been mentioned. Since restrictions changed, the last time Dianne was documented to be with Zoe and Alfie was in August... 8 MONTHS ago. And they supposedly only exchanged Christmas gifts a couple of weeks ago because they haven't seen each other. Not to mention the fact that Alfie said it was only Dianne they hadn't seen and not Joe, because we know that Joe was staying with them for a while when Dianne was at Strictly. Why would a big deal be made out of not seeing Dianne for 8 weeks and not Joe? And the fact that 8 weeks isn't even a long time anyway. I know he's not the sharpest tool in the shed, but would Alfie really be stupid enough to purposely expose the fact they've broken the rules? And then would supposedly 'media savvy' Joe and Dianne let him?
Of course Joe and Dianne don't document everything, and they could have secretly been having raging parties with hundreds of people for all we know, but I do genuinely think they've been pretty good at following all the rules. Dianne could have easily gone home for Christmas like Janette did, but she didn't because the rules changed and London was put in tier 4. Even yesterday with having Amy and Nancy over; yes there was a gazebo up, but we never actually saw them in it. All the photos and videos of them were outside. Maybe they did end up in it, who knows, but either way it's not even actually breaking any rules.
Honestly, I just think there's much bigger issues in the world than 3 people supposedly sitting socially distanced in a gazebo outside, tbh.