it makes perfect sense to me.
we've seen what happens when you don't have a clear message, people make their own interpretations and the whole thing collapses into a shambles.

we all know some people will be like - oh well if I can go to Sainsbury's to buy a new shirt then why can't I go to X etc
then pretty soon people are making non essential journeys all over the place and the whole idea of the fire break is ruined.

somewhat similar to the mixed messages we had from the Tories earlier in the year i.e. it was fine for Dominic Cummings to go to Barnard castle, which was followed by widespread breakdown of people sticking to the rules later