Thats why I wrote "as far as I know" and "what happened to me" and not "As I read in Airbnb rules".
Also I probably didn't have the same problem as you is because I only have apartments for 4 persons, so the times that it happened to me where 2 couples and never the second couple of the payment contacted me.
And what I wanted to express also (not English here and perhaps I didn't write it correctly) is that it helps if you tell the person doing the reservation (the first one) that the reservation isn't finished until the others pay.
Person makes reservation and does group pay, he pays, his friend doesn't.
1rst person "Give me your adress and phone number"
Me: You would be able to see it when the reservation is finished, your friend still has to pay. So the reservation isn't done.
That, In my case, made me wait only 8h of difference between the first payment and the second.
In my second case I simply wrote: "Your reservation isn't finished if the other party doesn't pay" as they didn't said anything (I wrote it in my language and being more nice than just saying that).
So thats what I wanted to say, that the others party never contacted me and thats posible make them pay faster.
Not saying that it's the best idea Airbnb had and perhaps with a little bit of luck they will end removing it (I don't think so but well... I can still hope).