Question about head proportions


Hello! I’m new here, this is my first post, I hope I’m posting in the right place!

I have a question about head proportions and how to determine them. In Andrew Loomis’ book “Drawing the Head and Hands” he explains that if we start with a circle and split it in half we get the brow line, then from there halfway up we determine the hairline.

Then the distance between the brow and the hairline is equal to the distance between the brow and the nose, also, equal to the distance between the nose and the chin.

However, as I took up his book “Figure Drawing for All It’s Worth” I found that I could not measure the head proportions as stated above when drawing the whole body because in this case you don’t start with a circle but instead you get the top of the head and the bottom of the chin as you split the eighths to get the rest of the body proportions.

So as I was looking for a way around this I came across people saying that if you split the head in half you get the line for the eyes and then if you split another half down you get the nose.

In which case it contradicts what I knew before. Hairline to brow = brow to nose = nose to chin. It becomes eyes to nose = nose to chin.

Can anyone help explain this? Are they just different techniques or am I missing something?