Still Re-Watching Angel Season 4

So why did the writers decide to make Connor 18, anyway? The age gap between him and Cordy would definitely be more noticeable if he was 16 or 17, and he would be more of a teenager. Was it so possessed!Cordy would not be guilty of statutory rape? Because they cared about that so much when Buffy was sleeping with Angel at seventeen. Come to think of it, how would the characters even know for sure how old Connor was? Did Holtz have an effective way to track his age in the middle of a hell dimension?