For what it's worth, all nations have rules like this about bringing in food. I remember being pulled aside as I entered the US a while ago because a sniffer dog found an apple in my hand luggage. This is about bio-security and it's taken very seriously by customs at all international borders and our own rules are quite clear; you can not bring in meat or meat products into the UK without checks and paperwork proving it is safe, that includes personal items. Checking around it looks like our current rules still allow people arriving from the EU with EU products to bring this stuff in - I guess that's part of Boris's deal, but the EU has a right to protect its borders just as we protect ours and they are only applying the rules to us that they apply to all third countries.