It might be a Windows* issue. I saw the “connect automatically” box checked initially at some point even after reconnecting without that box checked but after the steps above, my system is always connected to my network and not to any other unsecured network; so, the issue was not replicated entirely in my system. And this box was checked on that different network because I did so for this test, it is not something that just suddenly appeared on its own.
Nobody from the thread you linked above mentioned the wireless adapter model. Perhaps you may want to check with Microsoft*to see if they are aware about this issue.