Being a bit nerdy, I have kept a record since statistics were published of the daily government figures, both at UK, Wales, and local level, together with a comparison with those provided by the ONS. (My first listing was March 15th 2020 my last, at 4pm yesterday, so I do have a full picture. )
All I will say is you cannot cherrypick as there are many reasons why the figures may not be 100% accurate, eg computer maintenance, method of collation, weekends, Bank Holidays, all of which may add up to a fall and then a large increase on the subsequent days. The vast number of which I have noted at the time. My research has shown that over a few days it more or less evens out and is as accurate as you would expect it to be on such a large scale.
I don’t intend to bore you any further but would say that I am more inclined to growstuff’s views based on approximately 10 months figures sitting in front of me.