ANSWER:

No, this is not part of the sunnah and he will not be rewarded for that. Explain to them that sunnah is divided into two types; sunnah of worship and Sunnah of customs. The later is done according to the customs of the time and has nothing to do with being rewarded for doing it such as wearing a turban or riding a mule to go from one place to the other or sitting on the floor all the time and avoiding chairs! 

Leaving the hair long depends on the community and the people around you! If this is normal and done by REAL MEN as in some tribes, this is permissible. But if it is going to make a person stand out in a crowd or he is doing this to imitate disbelievers or women, then this is totally prohibited.

https://islamqa.info/en/answers/69822/braiding-mens-hair

How do I explain to people that although prophet had long hair, it is not part of a sunnah? Also the scholars in our country say it is sunnah to keep long hair. Will people following them be sinful by keeping long hair?