Yes, and that is also happening in this case, as was described previously. But when the traffic volume while in the pool reaches upper triple-digit Mbps volumes (at a 512kbit netspeed setting), even when dropping out of the pool, a corresponding proportion of residual traffic remains and takes time to die down.
And yes, there’s other effects as well, like I’ve seen traffic go up on a server this morning which I removed from the pool last night, before it continued to go down as expected. Even more pronounced on another system not long ago, both rate-/volume-wise as well as duration-wise, before it eventually subsided again.
No need for “shadow DNS”, the actual DNS has enough quirks and occasional malfunctions to cause this. Not to speak of client implementations. But as was discussed throughout this thread, and the previous one, this is unlikely to be the issue here.
Why is it so hard to grasp that in a zone with roughly 132,000,000 Internet users and less than 10 active servers, each one of them gets too much traffic?
I know, I can set the netspeed of my server in Germany to 3 Gbit, and will hardly get 2Mbit/s of traffic. But that is different in other regions of the world, where people can only dream of a client/server ratio like in Europe or the USA. This thread is about what the findings of your paper mean in practice when the pool is limiting clients to servers from their own zone only.