A website can have a PHP version selected but the install script will use the default CLI PHP version.
This can be overridden in things that are explicitly called in the install script. E.g. `php73 artisan config:cache` but can't be easily done when `php` is called from scripts in the site's code. For example in Laravel sites `composer.json` might include `php artisan package:discover` or `php artisan clear-compiled` which is automatically run after install.
Currently the only way to deploy a site that relies on a non-default PHP version during deployment is to `composer install --no-scripts` and manually call the appropriate scripts.
This is similar to my previous request roadmap.ploi.io/b/server-level-requests/set-php-version-for-users/