they are organized par "recently updated"- in theory. i have noticed in the past that not all content will bump the spot in the mosaic.i am not sure how well it works these days...the f4 are busy people so the issue might not be fixed yet
link many users however would prefer if we could arrange the mosaïque to our own preferences. we know which spots are active from our mises à jour feed so it would be plus convenient to be able to sort them in the order we need them. its been suggested and who knows..maybe the f4 will take our ideas into consideration.