As the OP assumes that diplomatic solutions have failed, the French may have tried to arrange such a solution but failed. The idea of a "phony war" also is unlikely. If a country does not really want to fight a war in the first place it does not declare war, engage in a few naval or land skirmishes, then call for peace. Declared wars have always tended to be extended brawls, the only "wars" that have resulted in low levels of violence have been battles fought over a specific disputed area.
If France lets the Anglo-Japanese alliance go on to severely defeat the Russians in the war (at the very least we can acknowledge the Russians are not going to get the status quo in such a war) they are put in the situation of being diplomatically isolated or forced into an alliance on the terms of another power like Austria-Hungary. Of course Austria-Hungary was a powerful nation, but it was always forced to defer to the Germans on big policy issues. Does one of the top four most powerful nations on Earth really want to be in the position of having to clear all its decisions with someone else?