sshing into a server only happens within one shell. Thus you can open tmux there and that's the only level of granularity you can have.

iterm window->iterm tab->ssh->tmux windows->tmux panes

With `tmux -CC` it lets you hoist that chain upwards and map the entire ssh session into an iterm window.

iterm window (ssh session) -> iterm tabs (tmux windows)

The biggest benefit for me is that you can then open another tmux session within the CC one and use tmux as normal

iterm window (ssh session) -> iterm tabs (tmux windows) -> tmux2 windows -> tmux2 panes

And then the normal feature of tmux is that it persists across ssh sessions. This also means that the entire iTerm2 window and all its tabs and splits are also maintained across sessions. I think my current layout on my main development machine that I remote into is over 3 months old.

Another point of view is that it decouples the state of your tmux tabs/panes from your terminal emulator itself. e.g. if you use this locally instead you could then terminate the entire iterm program and reopen it and restore the same exact window/tab/pane splits you previously had. This is a nice perk for restarting/updating iTerm.