WordPress Ignoring .user.ini

I have a server using Apache and PHP-FPM. The server hosts several WordPress sites with each site running as a different user and using a different pool.

I'm trying to configure the post_max_size and upload_max_filesize directives on a per-site basis by placing a .user.ini file in each site's document root. I know that the .user.ini file is being read because phpinfo() displays local values from the .user.ini file and master values from the main php.ini file. I've confirmed this using ini_get('post_max_size') and ini_get('upload_max_filesize') which both return the local values from the .user.ini file.

WordPress however, appears to ignore the .user.ini file. Plugins such as WP-ServerInfo and WP Server Stats display local and master values as the same, with the values coming from php.ini. I've confirmed this with ini_get() from within WordPress and Media Add New Maximum upload file size: 2 MB.

.user.ini is owned by the user running WordPress with 640 permissions.

I know it's possible to set directives on a per-pool basis using php_value or php_admin_value, but I'm interested to understand (and a little frustrated) why WordPress appears to be ignoring .user.ini.

Any insights are greatly appreciated.

Many thanks.

UPDATE:

The comment from @TomJNowell got me thinking. I did a search on what PHP CGI/FPM is passing to WordPress and found this post describing a similar issue with the Wordfence plugin.

I followed the suggestion of moving .user.ini from the document root to the /wp-admin directory. WordPress now gets passed the values in .user.ini. Conversely, phpinfo() doesn't get these values as it's in a script run from the document root, which makes sense.

The post went on to suggest moving .user.ini back to the document root then creating a symlink to it in the /wp-admin directory. Now both WordPress and phpinfo() get the values from .user.ini.

Not sure this last step is strictly necessary as the directives are for the benefit of WordPress, but it does tie-it-up neatly.

I'm also unsure why my original setup doesn't work, but having .user.ini (or a symlink to it) in the /wp-admin directory does. Maybe this is more of a hack than the correct way of doing it, but I'm content for now that it works.