Plot hole: The whole basis for replacing Admiral Broderick with John Wayne as operational commander of Sky Hook was that Admiral Broderick was deemed a failure. Wayne took over, planned for what looks like a week or so and launched an attack. First point - the Japanese had evacuated the island. It's pretty hard to miss the evacuation of 15 or 20 thousand soldiers by the IJN which would have made multiple large sorties over a period of several days. Also, there would have been massive explosions and fires as the Japanese destroyed facilities and supplies rather than leave them behind. (Check out the real evacuation of Guadalcanal during WWII - the IJN operation was so big we thought they were reinforcing the island) Second point - seems like Admiral Broderick's approach, no matter how incompetent it looked, must have worked. The Japanese gave up and left and it must have been as a result of Broderick's efforts. An evacuation like this takes time to plan and time to execute. The evacuation was decided upon prior to Wayne's arrival (Broderick had already won) and took place right under his nose (complete reconnaissance failure by Wayne).
Plot hole: As Torrey's task force seeks out the Japanese, the JL talker on the bridge informs the Captain that the starboard lookout reports a ship on the bow. Immediately everyone goes over to the port side to see the vessel, which appears (through the binoculars) to be about five miles distant. Poor lookout discipline.
Answer: One Star rank wasn't formalized until 1943. Rear Admiral lower and upper wore the same 2-stars.