Say, russian player needs healing, so he uses the “I need healing” emote. Except for the rest of the team, they will recieve the message in the language of the sender, that is, in russian. Unless they speak that language, they will have no idea what their teammate is requesting.
In Vermintide 2, emotes were recieved in the language of the reciever, not the sender, which made all the sense in the world. Changing this in Darktide puts a language barrier between players.