How to set the appropriate customer_locale on order entity

[sansems]

According to the API specs the customer_locale field is part of the order (see here https://shopify.dev/api/admin-rest/2022-04/resources/order#resource-object), this is also what's been advertised to be part of the order (https://shopify.dev/changelog/locale-fields-are-now-appended-with-language-and-country-codes)

However i see something totally different when i look into the values we actually get in the the customer_locale field on the orders we receive from many Shopify shops through the through the Order API's. We get some weird customer_locale values that are not valid according to the IETF BCP47: Testify the following image:

This seems like a bug to me, but how can we get the actual customer_locale in the order?