It seems they identified servers via the discovery feature, which servers need to opt into (and I think be recognised as a "community server"? Though that might

It seems they identified servers via the discovery feature, which servers need to opt into (and I think be recognised as a "community server"? Though that might be out of date). I guess this is better than just scanning the web for invite links, but it does mean that probably most of those game modding servers were not included.