In the article they actually talk about that "wiggle" As a HS he was a QB, he actually signed with Virginia Tech as a QB and only was moved to Safety there...... After playing Corner back for a while too.
The explanation is really just freak athlete. He's big, he's fast, he's strong and he's got twitch.... now your not gonna mix him up for Earl Thomas but Kam has enough to dominate as a SS.
His college DB coach said that the nfl will try to make you a line backer..... resist it, he has everything you need to dominate at Safety