Custom S3 endpoint not being recognized

When submitting an obviously bogus S3 endpoint URL (see screenshot below), I get an error which says, “Insufficient permissions to create bucket”. How is this possible?

My goal is to point the blob store at my local minio instance, but it appears to be ignoring the “Advanced Connection Settings” completely.

Currently, only AWS S3 is supported:

https://help.sonatype.com/repomanager3/configuration/storage-guide#StorageGuide-Requirements

Why do I have the option to input a custom endpoint if custom endpoints are not supported?