My install flow is not as you mention. With -wpsubdom install, after I login, I never get the installation choice for subdomain or subdirectory. I have uncommented the line in the wp-config.php file, and then I just get an error (403 error I think).
I tried a second time, install from scratch on a new DigitalOcean droplet, same issue, no choice for subdomain or subdirectory after logging in to Wordpress, but I can login, but the admin area is a normal Wordpress install. I uncomment the lines in the wp-config.php file, now I have redirect error. I posted a question about this already?