Why AWS credentials are need?

[aik099]

I've been using this library for a while, but I still don't understand why you need to specify awsAccessKey and awsSecretKey, when only lwaClientId + lwaClientIdSecret + seller_oauth_refresh_token are used to obtain an access token and that token is used in every other SP API request.

From the code I see that they are used for HTTP request signing, but I've tried to use some dummy access key/secret key and my SP API call still worked.