I think the emphasis there would be on the "interaction" part. I'm sure the ESRB could still rate the actual content of the game the same as usual, they just can't judge what you may or may not experience from other players.
English
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Online "Interaction". As in your interaction with other players, is not rated, as there is no way to rate what other people will say/do to you in game. All the game content (NPCs, missions, scenarios, etc) will be rated accordingly.