Does Slack external content connector allow search on discussions or just files?

We have configure Slack external content connector in our dev instance and crawled two slack channels.
When searching, the results seldom comes up from this search source and when it do, it's only attached files.

I can see that the crawl found "documents" but it's night and day compared to our connector to Confluence which works really well.

What can we expect from Slack external content connector?
Can it find answers from discussions or will it just index files?