You're correct. In the linked Wichita Eagle article it says
After all, as Kobach pointed out: Elected officials in Kansas are required by law to be legal electors — meaning legally registered voters.
BTW there's a lot to shake your head at in that article. The stupidity and lack of education of not just this guy but apparently the whole town. They didn't know he wasn't allowed to vote. He wasn't sure who he voted for, he just always voted for the (R). Plus the whole town loves this guy so they're all mad at Kobach. That county went 80% for trump but they're all upset that they're having the day they voted for.