Elastic search s3 plugin and bucket name

Hello
May I please get some clarification on my observations regarding the S3 plugin and bucket names?

I have observed with Elasticsearch 7.10.2 and the s3 plugin that if i don't provide the bucket name in all caps the endpoint cannot be resolved. Elastic tosses a read timeout.
"Caused by: com.amazonaws.SdkClientException: Unable to execute HTTP request: Connect to elastbuc.localstack:4566 [elastbuc.localstack/92.242.140.21] failed: Connect timed out",

I am using localstack as the S3.

When i create the bucket its in all lower case. eg "elastbuc"

thanks