I dont know if the excercise is pointless. Child obesity is on the increase in many European countries, Britain and Norway included.
There is a pilot project here (in Norway) where the kids in secondary come to school 1 hour early 3 days per week for an additional hour of PE, mainly circuit training. In primary, they have one hour of hip hop and one hour of baseball extra after school, for the same reason.
Children sit still a lot more than before, they are interested in nintendos, tv, pc games, etc.
Any stocky child is a potential overweight child with bad eating habit and a passive life.
Imagine the cost of making seats in airplanes larger, ambulances bigger, etc, to cater for an ever growing population, who eat the same amount of calories as their grandparents did, but sit on their arses a lot more. Be it in an office job, or sitting for hours receiving learning.
In my honest opinion, dont feel patronized, be glad that the issue is tackled nationwide, and it is not only your daughter who gets such a letter.