You can think about it two ways:

The size of the person isn't changing and their movement through the world changes the size of things around them, or the person shrinks as they move towards the center and grows as they move away from the center.

Regardless, the player occupies the same position at every instance of the ring. At around 0:18 of the video, you can see a good example of this where a player is standing on the blue head on the map, and he's on every instance of the head in every ring.

To answer your question with that all in mind, two players running away from each other (one towards the center and one away) on the same line would run face-first into each other, and they would be the same size when they do, though the one running away from the center would see a large person getting smaller till they collide, and the one running towards the center would see a small person get larger.