Hi @ryanerwin
Seems you are not fully understanding containers and docker a bit; so let me help you out.
Redis runs by default in the standalone container on port 6379:
cd /var/discourse
./launcher enter app
apt install net-tools
netstat -an | grep :6379 |wc -l
74
Now lets exit the container and check netstat for Redis:
exit
root@localhost:/var/discourse# netstat -an | grep :6379 |wc -l
0
So, you can see that Redis is listening on localhost inside the container; and localhost inside the container was (is) not exposed outside the container.
Hence, if you have many standalone discourse containers running, there would not be any Redis conflicts between containers because Redis has not been exposed outside each container.
That’s why it’s called a “container”… 
Every socket inside the container must be explicitly exposed to be available outside the container.
Hope this helps in some small way.
Note that unix domain sockets are very cool… I only addressed your comment about perceived Redis conflicts between standalone containers and did not address the unix domain socket topic.