What Is The Normal Head Measurement Of An Infant With Torticollis?

Hello,

My 4 months old boy has torticollis, which leads to a flat spot at the right side of the back of his head. He is being treated for that but I have a question about head circumference measurment. He was born at 37+6 weeks with HC of 33 cm.
at one month old it was 36.8 and at 2 months old it was 38.7.
Since than the flat spot started and it is my understanding that because of that, one must seek the largest possible circumference by moving the tape around his head, because he has an "abnormal" head shape cos of the torticollis. Before his 4 months appointment I did just that and got a measurment of 41.5 cm. but the nurse just didn't considered the flat spot and at first said that his head didn't grow at all since 2 months old. I asked her to measure again and than she said it is 41.3.

Am I wrong by thinking that one must move the tape around the head 3 times in order to find the largest possible measurment?

Thank you