that rule has been in place since they put the rules in due to legality of copyrights.
it does relinquish a lot of rights to Epic but I’ve never seen them abuse it.
it basically means they can show it on the Twitch Stream & publicize it however they want to, such as shows, conventions, videos etc. without worrying about copyright infringement or being sued basically.
as I said above I’ve never seen them abuse it in any form it’s mainly to protect themselves.
what you make is subject to public exposure so if you’re that worried about it then don’t use it or don’t participate, it’s up to you.