Its not really a change, because its a fix to something that didnt happen in vanilla, xrealm and the honor system existed together for a very short time. And the cross realm premades were ruining the games for the other players.
You can blame the mega discords where they would queue up 200-300 players at a once, opening up 15+ bgs and only joining 2-3 of them, leaving alliance players to play 15v40 in the remaining games.
It was great for people who did premades, but at the cost of making battlegrounds completely unplayable for people not part of the premades.
Losing battlegrounds because you got beat by the enemy is fine, but being griefed by your own faction like this... are you really suprised that they wanted to stop it?