Yes, Physics… which is why it doesn’t make sense to most of us and that is ok. In the example i posted there are 3 physically closer zigbee repeating devices it should be connected to, but due to a bunch of stuff i cant see and too time consuming to measure like interference from my neighbors or even my wifi or Bluetooth the Guest AV is the best device to connect to and its on the complete opposite end of my house 2 rooms away.
There are so many things that can cause interference in a zigbee network it can be really difficult to figure it out even when there are vast differences in signal and only 20cm distance. Below are some articles that have helped many with your situation find some solution. You may even find out that you have so much interference on the 2.4gz bands that zigbee is not a good fit for your home and zwave may work better due to less interference in your home in the 800mhz bands.