You don't have to use tmux as a daemon manager to find this change annoying. The way we do development where I work is by having two people ssh into a server,

You don't have to use tmux as a daemon manager to find this change annoying. The way we do development where I work is by having two people ssh into a server, and open a joint tmux session. These sessions generally last a week or more, and you generally log out of ssh daily. Or even if you're not pairing, just being disconnected over lunch is a long enough time for SSH to disconnect. Finding ways to overcome that (besides changing the systemd config) are even more duck tape fixes. Automatically terminating processes when a user logs out is a bad default. Sure, leave it as an option because there might be some people that would find it useful, but changing the default without a good reason is bad policy.