For anyone who's been confused with blenders hair particle settings like I have, if you want to randomize the hair length on your model when using hair particles the hair length in the emission settings is your maximum hair length. Changing the children length below 1 will shorten the hairs but increasing the threshold slider will gradually bring more of those maximum length hairs back in. Imagine the emission hair length like a maximum and children length as a minimum with the threshold as a slider to control the factor. Note: if the children length is at 1 it will not randomise length as you have no minimum length value.
Hope this helps some of you exploring the hair features!
hair with maximum children length value applied (emission length 0.02)
Hair with children length value of 0.2
Hair with children length 0.2 and threshold at 0.03 (increased threshold = more long hairs so higher values may not appear that random)
