Posted elsewhere, they have tightened regulations to clamp down on the "franken-shoes".

40mm stack height maximum One carbon plate only (some shoes were including a second). Must be on sale to the public for < 4 mths before the race in question

Puma makes a shoe that's non-compliant with the above (two plates, not sure about the stack height), for what it's worth.

nope, nike vaporflys are super popular. There are usually limits on stack height for many marathons though.