There's nothing surprising to the ranking being similar. Old accounts don't use classic, they use the normal HN homepage like everybody else. Which means, they

There's nothing surprising to the ranking being similar. Old accounts don't use classic, they use the normal HN homepage like everybody else. Which means, they see the same top links as everybody else, and upvote them, like everybody else. In other words, /classic is remarkably useless. It might have been useful when it was created (11 years ago!), if a sizeable part of those old accounts would use /classic, and only /classic.