Length seems to be a matter of taste and comfort.

I recently ordered a new 5-yarder, sending my measurements calculated very carfully, both on my body and on my other kilts.

I asked for waist-to-knee : 22 inches.
Reply from supplier : this must be a mistake; it is too long for a man of 66 inches height.

Go understand !

Looking at old British military photos, I see kilts were worn just above the knee.
Looking at North American kilt wearers, it is often below the knee.
I was told, 40 years ago, a kilt should barely touch the ground when kneeling.
Today, some kilt-makers recommend the bottom edge should be an inch & a half from the gound.

Added to this, we are all shapes and sizes and all wear our kilts in different ways. What may look too long one one man will be appear to short on another.

Martin