The fact that Meb doesn't have a PR machine like Bolt shows here. It is a mistake for Meb to suggest a challenge. Both Meb and Bolt would look horrible at a distance that they are similar at. Meb would look slow and Bolt would look horrible in the final hundred meters even if he won. Why would people want to see these two figures run well behind what Rudisha could do? Meb and Bolt are just too far apart to be entertaining on middle ground.
Now, stack Bolt with Rudisha somewhere between 400-600m and that would be exciting.
But hey, don't let me interfer with fantasy . . .