Please give any daleel that this is a part of wudu.Even a weak hadith.As this is mentioned in a response of one of your questions about how to make wudu Jazakallahu khairun.
Answer
It is Mustahabb to wipe the back of the neck during Wudhu.
and Allah Ta’ala Knows Best
Mufti Ebrahim Desai
FATWA DEPT.