You seem to misunderstand /scid and /scon, /scon N use the Nth connexion, /scon 1 use the first connexion, /scon 2 the second etc.
For /scid it's completely different, each connexion has an associated number called connexion id, it can be anything, you should never assume the first connexion has a connexion id of 1.
Also, note that /scon and /scid double evaluate their parameters, in your case it's working because you only have one command, when mirc see the condition, it just see :
if ($window(Status Window).state != maximized) echo 4 -a yes
because the { and } has been evaluated
//scid 1 if ($window(Status Window).state != maximized) { echo 4 -a yes | echo -a yeah }
would not work as expected