The detection to see if the config.php and admin/config.php isn't accurate.
In the installer:
<basedir>/config.php Writable
<basedir>/admin/config.php Writable
But they definitely are not writable, and get the following error when attempting to progress:
I fix the perms and continue as normal.Warning: config.php needs to be writable for OpenCart to be installed!
Also, it might be an idea to include some check code in the main opencart app (or at least the admin modules) warning you that the install directory still exists and should be removed. I fear that there would be quite a few people out there who get OpenCart installed, jump in to the admin console to start playing and forget all about the install directory removal (if they see it in the first place).