The issue is PHP-FPM (FastCGI) only and it's vulnerable from outside only with nginx.
The vast majority of PHP 7.0 installations don't use FastGCI and don't use nginx but Apache simply because people used 'apt install php' (or 'yum install php') to install it.
The vast majority of PHP 7.0 installations don't use FastGCI and don't use nginx but Apache simply because people used 'apt install php' (or 'yum install php') to install it.
So imho, the impact is very limited.