If that's the case, then what you gave is the reason, is it not? A post made 1 minute ago will have 100x the score a post made 100 minutes ago, and this boost in score at a young age will cause a young post with only 1 or 2 upvotes to hit the first few pages for a short time, giving it a chance to get more upvotes if it's a good post.
No, because there are other factors mixed in, such as requiring a minimum number of upvotes by contributors not recognised as being in a voting ring, and beating the "gravity" factor. There are also penalties applied for certain types of posts and sources, boosts applied for certain types of posts, and penalties for some conditions. For example, when a post hits 40 posts, if the number of comments exceeds the number of points, a "probable flame war" penalty is applied.
So it's not the case that posts from the new page "get mixed in" to the Front Page, they get there on merit based on getting enough votes in a short enough time. To say they get "mixed in" implies that they are simply plucked from the "Newest" page and put on the Front Page regardless of votes. And that's not the case.
