Truth: some Linux distros have a "wheel" group.
Truth: this group is used as a list of people with elevated permissions
Truth: one of the elevated permissions often assigned to this group is the ability to become root, especially with sudo
Falsehood: all users on a Linux system are members of the "wheel" group
Falsehood: one can add oneself to the "wheel" group without having permissions already elevated above regular user status
tl;dr: someone misunderstands groups and called it a vulnerability