I think this video can answer your question: https://www.veritasium.com/videos/2021/9/30/your-dna-is-alre...

I don’t remember the exact details, because I have watched it long time ago, but they don’t need an exact match. Actually it’s more scary - if your distant cousin has DNA “in the system” - you are in it too.

This 1M DNAs may “help” match an order of magnitude more people.