> Your contention is that any and all poor performance is due to the pandemic, not in any way related to Brexit?

Your interpretation of the parent post is mistaken. They are saying that if you wish to try to isolate the effects of Brexit from the effects of the pandemic (and the recovery) in your analysis you should compare 4 years' data.

I'm not sure the initial comment lends itself to that reading, but it isn't clear it lends itself to my initial response either, so I'll switch over to your more charitable reading. Thanks!