The BGs are xrealm, yeah. They had said before Classic came out that it’d be xrealm, because they’re following the reference client (1.12) and that’s what that client had.
But as BGs were released early in what was later called “phase 2.5”, the xrealm we got was literally ALL servers of ALL languages mixed together into the same matchmaking pool. You could be matched up with Russians as well as all the other languages.
That made lots of people complain, and shortly after they separated the Russian realms from the matchmaking. However you can still get matched up with all the other language’d realms, like Germans etc.
You can still get matched up against Russian realms however. But they’re limited to only being matched up on the same team as other players on Russian realms.
So basically, there are no battlegroups, unlike what it was like in 1.12.
So the matchmaking we have now is like retail’s. Kind of.