If I look at the source of _tmux:
https://github.com/zsh-users/zsh/blob/master/Completion/Unix/Command/_tmux#L628
(and my local _tmux), the options start from -A.

However, when I run tmux new -<Tab> I only see:
 -- option --
-D  -- in case of -A behave like attach-session's -d
-F  -- specify format of output
-P  -- print information about new session after it is created
-c  -- specify working directory for the session
-d  -- do not attach new session to current terminal
-n  -- name the initial window
-s  -- name the session
-t  -- specify target session
-x  -- specify width
-y  -- specify height


Why are some options missing?

-- 
have a nice day
-jck