All three would be extremely beneficial. The more information we can gather about active processes the better we an support.
For us when IT needs to make a change to a server it won’t do me any good to have all users show which server they are logged into as I won’t be calling around to our possible 85 desktop users to ask them. Instead I would like a quick and easy way to know out of the 15 sessions shown in ECA - which server are these users logged into. We used this info back in our E9 world quite frequently.
With a load balancer scenario, who cares what app server they are on if you want to recycle an app server? I assume you are using non sticky connections through the LB so the client will just reconnect and voila, no lose of anything.
The only caveat is the Task Agent servers processing long amounts of work. Those you need to treat differently as you need to trickle down their work and point them to new instances. Nothing I have not had to handle 20 years ago on rolling upgrades.
Yea, that was a bit of a trick question 
The point is there are all three scenarios.