Just to update here in addition to the Github issue, Matt has worked out some other aspects of URL rewriting in relation to serving serving static assets and reverse proxying (e.g., to PHP).
In v2 now, the following alone may be enough to have *.php files processed by PHP and other, non- *.php files served directly:
https://example.com
root * /path/to/public_html
php_fastcgi unix//run/php/php7.3-fpm.sock
file_server
If the PHP software requires particular URL rewrites, something like the following (which is for Craft CMS) can be added:
try_files {path} /index.php?{query}&p={path}