"Range" RequestHeader and UnityWebRequest

Unity Engine
,
1 
var download = UnityWebRequest.Post(url, form);
download.SetRequestHeader("Range", "bytes=0-100");
yield return download.SendWebRequest();

This gives full of data. but range is “bytes=0-100”. What is problem in these codes?

2

Isn’t the Range header other than the GET method out of specification?
The RFC states that Range headers in requests other than the GET method should be ignored.