Hybrid Delve - Content surfacing and signals from on-premises environments

Hi,

We have started using the cloud ssa in a SharePoint 2013 farm and can confirm that on-prem content appear in Delve even if you don't search.

We can favorite on-prem content and add to boards.

I suspect that the only signals available for the on-prem content is comming from the hybrid search itself, but it's just my theory.

I see documents from a team site in SharePoint 2013 marked as "Private document" Modified  March 10, and I see a word document marked as "Popular".

Non of these items appear with a reference to someone who has edited, emailed or shared with me.

I expect some of the documents to appear in Delve because they have been in my search results in SPO, but the popular one hasn't.

The whole experience is a bit black box magic for now.

I suspect on-prem signals are fed to Delve every time a document is re-crawled and cloud index updated, but I cannot prove that theory.