I am not sure what the legal position is but a declaration implies you must keep the calf alive for 8 weeks. I guess the declaration means that it is not the dairy industry's problem - or Arla's for that matter. The early slaughter or euthanasia of that calf becomes a beef industry issue.
The timeframe means that you will have weathered the most expensive part of the calf's life and you would be weaning it or close to weaning it so would be unlikely to slaughter the calf at that point. Whilst there will be unintended consequences to this, I think it is right that the industry takes the issue seriously as it is wounding for reputation and they have to start somewhere.
It is teh word you use, "implies" that is kind of where my question was arrived from.
I fully understand your point, and have no argument whatsoever with it, however, when I saw 9 week old calves going off to slaughter, I question the rationale somewhat!