Bureaucrats have their own way of thinking. Whenever there is talk about cutting back or lowing authority, their first inclination is to “cut the meat and protect the fat”.
Say you have a dozen programs, only one of which is popular and efficient, whereas the other 11 are wasteful and bloated. So you offer to cut the popular one. This puts pressure on those who want to cut.
In this case, there are likely at least *some* EU programs that work well and are liked by the British. So they will offer to end these immediately, while insisting that the unpopular and stupid programs can either not be eliminated or can only be eliminated at great cost and time to Britain.
And, it will get worse. Popular goods flowing back and forth will be curtailed, while unpopular things, like immigrants, won’t be. They will even make things like TSA lines for people who want to cross the border in either direction. It is, and will be, pure harassment.
Couldn’t work like that. EU programmes aren’t enforced in Britain by EU bureaucrats (they haven’t the power), they’re enforced by British civil servants in British government departments. The moment a British government tells those civil servants to stop enforcing them, they’ll stop.