S3 is is specific service. Sometimes it behaves like regional service, other times like global one.

Try to remove region parameter from your S3 client. Connection will be created to default region for S3 (us-east-1).

Presigned URL generates temporary security credentials and embeds this into URL. This involves IAM service and STS service.

IAM is global service and S3 has its own special behaviour. I have no better explanation. Try S3 client without region.