Zend certified PHP/Magento developer

Forcing Dynamic configuration

We often in our projects use the app/etc/config.php file to force some admin configuration we don’t want the end user to be able to modify.
This time we’re trying to force the configuration for a dynamic field:

https://i.stack.imgur.com/hNC4u.png

However it is not working at all, the field becomes grey empty:

https://i.stack.imgur.com/2rl2M.png

We’ve tried setting the configuration like so (by copying the value from the core_config_data table):

'hyva_theme_fallback' => [
                'general' => [
                    'enable' => 1,
                    'list_part_of_url' => '{"_1612520818489_489":{"path":"checkout/index"},"_1612520843057_57":{"path":"paypal/express/review"},"_1612776810949_949":{"path":"paypal/express/saveShippingMethod"},"_1645247921478_478":{"path":"paypal/transparent/redirect"},"_1645249412397_397":{"path":"paypal/transparent/response"}}'
                ]
            ],

It’s working fine for every other admin field type but this one. Is it actually possible to do this ?