To answer the question, I occasionally browse new and upvote posts. Probably around 30%-40% of my upvotes are from new. However, my understanding was that newer posts got mixed in to the front page, so posts worthy of upvotes have a chance to receive them. Example: this very post, as of time of me writing this, has only 10 upvotes and was on the front page for me, in between two posts with hundreds of upvotes.
That's common, as the "score" for a post is (very roughly) points divided by time. So a newer post with fewer points can still have the same "score" as an older post with many more points, giving the effect you've seen without the cause you posit.
So what you say about the mixing may be true, but is not evidenced by the example you've quoted.