File Poller on S3 Only Output on Change

In the documentation, the section “Only Output on Change” mentions that it runs if there is a change in the contents of the directory. Is this strictly the timestamp of the file(s) based on the pattern or are the contents of the file checked somehow as well?

I have tested changing the contents (which in turn changes the timestamp of course) on a local file directory and it works without issue. However, when I test on S3, generating a new file but with the same contents, the File Poller does not seem to detect the change.