If a WFN or LFN penetrates deeper than a RN it is only because the RN tumbles during penetration, and they are VERY likely to tumble it not driven at enough speed to get high RPM's with the rifling of interest, for stability. In other words, RN's work fairly well at the velocities produced by dangerous game rifles, and have found good favor for many years, but only because no one realized a flat was far superior in every way.
An RN can penetrate easier and farther, depending on nose shape/impact velocity, because it slips through flesh doing little damage. But NOT MUCH farther, and if impact velocity is low enough, they can penetrate much less due to friction of tissue sliding along the bullet sides, whereas a large flat nose splashes tissue out of the way and flies through in a vacume. (Which is your answer.)
The most important reason for large flat noses is to make game lay down promptly after the wide flat rips a fast bleeding wound clear through. By promptly, I mean by time the gun comes out of recoil so you can see it again, or milliseconds thereafter.
At worst we want the trail it leaves by to look like your bullet went through a bucket of red paint.
