I'm not them but I added AWS Organizations support to moto because we needed to test all of the child account enumeration APIs. If I would have had more time/energy I would have continued my tilting at windmills to have it honor the actual $(aws sts assume-role) keys, too, since hopping between accounts in the org via the injected IAM Role was also very critical to the product at the time

I got a lot of enjoyment out of https://awsteele.com/blog/2020/09/26/aws-access-key-format.h... at the time, too