I am not sure why either. I think it is just to boost your metabolism to keep the weight loss results good. But lots of us choose not to have the break and carry on through. I dont think it makes any difference. However some people still have a good loss on add a meal week and then it boosts their metabolism to continue with the good losses after that.
I think it's more to do with the fact we're not being monitored through our progress.
NICE guidelines say to AAM after 12 weeks, but on LL you have your blood pressure monitored every 4 weeks, and you have counsellor guidance.
I guess Exante are covering their backs with the 'we told you to AAM after 4 weeks and you didn't so it's your fault you collapsed' sort of thing if you choose not to follow their advice