Did you think that the faction war in WoW Classic could never actually be won? Turns out it can, since it appears that the entirety of the Alliance population on the Flamelash server has opted to nope right out of the faction imbalance. This has prompted players to shift between arguing that Blizzard is to blame for not balancing the factions or free transfers properly and that Horde players are to blame for turning the game into an unbalanced gank festival that made the game functionally unplayable for anyone who made an Alliance character.
The lack of any official realm census obviously makes it impossible to absolutely verify whether or not the server is really devoid of Alliance players, but in this case the perception is almost as important. Players have also noted that while battlegrounds will allow for interactions with the PvP system, they will not bring back the open-world PvP, although we somehow doubt that any hypothetical Alliance players will be particularly upset to see that gone.