It was the Japanese Navy that wanted to go south. The U.S oil embargo was hurting the Japanese badly. When the final plans for Pearl Harbor were put in motion, the Japanese fleet was down to something like a 90 day reserve of fuel.
Japan went to war to seize the oil fields of Indonesia. The inexorable logic [to them] of attacking the Dutch was the inevitability of Great Britain jumping in, and the high probability of the U.S engaging in hostilities. So the Navy won the battle, to go south. And since the principal threat to their operations was the U.S Pacific fleet, which FDR had moved to Pearl, Yamamoto decided to preemptively strike there.
Interestingly, the Soviet spy in Tokyo, Richard Sorge, was able to ascertain that the Japanese were not going to attack Siberia, allowing Stalin to withdraw the divisions that counterattacked the Germans in front of Moscow, drove them back, and broke the myth [in WW II] of German invincibility.
There is a lot of truth to what you say, but, the short, disasterous war in Siberia and Mongolia resulted, I think, in the Japanese signing a nonagression pact with the Soviets, which, unlike Hitler, they honored. the Soviets broke that pact in 1945 at Roosevelt’s urging.
It was that nonagression pact that freed up the Soviet forces under Zhukov to move west to stop Hitler’s forces. I think it was Zhukov’s posting to the remote regions of Siberia that saved him from being purged, which probably saved the Soviets from total defeat from both ends of their empire.