Pantheon's approach to wp-config.php
Pantheon's default wp-config.php first looks for wp-config-local.php, confirms it is not running on Panthen and then loads wp-config-local.php but bypasses everything else, which means that for local development you'll need to duplicate and maintain all the default settings into your local config.
Further, Pantheon does not provide a clean method to differentiate between their various environments your code will be running on, which can become especially challenging if you use branches.
Yes, Pantheon provides configuration in $_ENV variables (I wish all WordPress webhosts did this) but you still have to roll-your-own alternative to wp-config.php, which from experience we can definitively say is a rabbit-hole you probably don't want to waste your time on.
And even if you do roll your own special wp-config.php it will almost certainly be incompatible with other web hosts that your future clients will almost certainly demand you use instead of Pantheon because, for example, they once read that Gartner said a different managed WordPress host was the most secure (3 years ago.) At least that has been our experience.
But if you are running your WordPress websites on Pantheon don't despair; there is a better way!
Use Better WP-Config instead!
If you are from Pantheon, please reach out to discuss how we can collaborate to make Pantheon much better for your customers by incorporating and Better WP-Config into your WordPress hosting service and provide us feedback so we can make Better WP-Config support your service even better that we already do.