Waitrose (and its partner, John Lewis) is/are in severe financial trouble and this virtue signalling will be part of the reason why. They refuse to give even ecologically acceptable paper bags though they are willing to sell a plastic bag to whoever wants one. In the case of my last shopping trip - where I brought my own bags - everyone ahead of me bought new bags.
Additionally, they are pushing 'Veganuary' (with its associated massive profit margins compared to those of meat products) and most of the food ends up being neglected and yellow stickered.
Their well publicised spat with their food magazine editor, William Sitwell, whom they fired for teasing a vegan exposed their soi disant 'principles'.
As for telling paying customers what to eat in their cafe, words fail me.
They are a business and they should be listening to their cutomers not preaching to them. If they carry on in this way they will fail.