sharepoint online – Is there a way to share/link to files on a hub site with an associated site, or vice versa?

My organization is reviewing a way to move forward with file storage and one of the scenarios we will face is content that currently exists on a classic Team site in SharePoint Online that we would like to somehow associate with a Microsoft Team, specifically with the SharePoint Online backend site for the team that gets automatically created.

I had thought a Hub site would be a way to do this; by setting the Microsoft Teams-created SP site as a Hub and then associating the classic Team site with it, I was hoping to be able to see the content linked or available between the two sites… because that seems to me to be the prime use in something like linking a site to a Hub (otherwise why leave the classic ‘site -> subsite’ schema of yesteryear which worked fine?)

However, I cannot seem to find a way to link content between the two sites, or make content from one site available in another. Is there some way to do this? I can’t even search for content in one of the other sites as this article suggests:

Search within a Hub

Once you create a Hub and connect other sites to it, you will notice that a Search Box on the Main Hub now searches across other sites within a Hub. This is amazing!

'Search Across Sites' image

(I can’t even find that “Search Across Sites” box/option. I only see one Search field centered at the top of the viewport).

I guess I’m not really seeing any point/use in associating sites with a Hub site at this point.