I did explain this in my previous post :-) If you connect to an SSL server, mIRC will maintain the SSL state of the status window from that point onwards for security reasons, unless you connect to a different network.
mIRC used to do what you are requesting. But users complained that if they connected to an SSL server and mIRC tried reconnecting to the server, and the server contained a range of ports some of which were not SSL, mIRC could switch to a non-secure port. So I changed mIRC to maintain a secure connection, which is a priority for security reasons.
To get around this, you can add servers with different group names.
