Heads are judging because parents are not the only stakeholder they are answerable to.
I understand why they are judging. They are being told to. again, it's the rule I am questioning, not the enforcement.
That, sorry, little chilli had 9 days off so far and to take another 10 would be inadvisable
I have not explained such a thing to a parent. But it appears that saying it so politely and clearly as you have done should be fine. Parents can take or leave it.
The trouble is that the head will say this even if the child is doing fine because the government says it's "inadvisable".
its a really bad idea to take your kid away two weeks before GCSEs start?
Said so well. I hope all heads say it that way. Again, a parent can should be able to take the advice under consideration and make up his/her own mind.