Personally, I think the obsession with shook swarming is the problem.
Just shook swarming the infected colony may 'cure' it (depending on what variant foulbrood they have) but that causes confused nurse bees to beg their way into neighbouring colonies hence risking the spread, whole apiary shook swarming will just end up with bees mixing and matching even more. It would be a step in the right direction I think if they started compulsory destruction of any individual colony found to be infected would be a step in the right direction as there is always the temptation to 'save' the poor dabs.
Had quite a discussion on the subject during my DASH visit on Friday, I honestly said (giving I haven't been unlucky to have met the issue in my apiaries) that if I was given the choice, on detecting foulbrood, I was minded to not faff around but destroy that colony, 'But but' was the reply 'what if we only find one singe infected cell?' so you see the mindset is there to bang our heads against a wall for a few times before finally biting the bullet. My answer was still yes BTW