bobbing your head around when you're out of range then rushing in on a straight line isn't head movement (aka the Rashad Evans)
it simulates it to people who've never trained a day of striking in their life and is television friendly but it don't do much
very occasionally Cain dips to his right when coming forward while pumping the jab but he usually just comes in square and on a straight trajectory, it's how Kongo caught him flush it's why he ate so many jabs from JDS when JDS could still throw jabs. doesn't take his head off center