You're right about legal non-citizens voting but you're misreading the words "Illegal Alien Voters" in the title.
Since the article's statistics are of the "adult non-citizen population" it clearly means illegal "alien voters" as in all "aliens voters" (non-citizen voters) are illegal voters.
I was just trying to clarify.
Both non citizens and illegal aliens are not legally permitted to vote in the presidential election. But they do.