This is expected result. The docker version uses an environment variables to get useful configs. So, you do not need to change the internal port in the config.yaml of docker setup unless you uses a host network instead of default NAT.
Usually you should change only a left part of the port mapping (external port), but not the internal one, because each container is isolated from the network (in the default usage): -p 28968:28967
You should NOT modify the port in the config.yaml unless you using a Windows GUI.
The Windows GUI is not a docker container, it’s not isolated from the network, so, you must change the port in case of the second Windows GUI setup on the same host. And do not need to do so, if these setups on different machines in the network: you can forward the 28967 to the first machine on 28967 and 28968 to the second on 28967 too, because they are on different machines.
You can read more there: