Who cares? No one made the claim that these guys were great fighters, what's the problem with just appreciating that this takes skill, stamina, and a whole mess of speed.
And "The Octagon" isn't exactly the supreme test of fighting capability, either. Everything has it's own adaptations, the "realest" of them all would be on the street...Would you really want to take a fight to the ground if there's broken glass or hypodermic needles on the floor? Would you want to breakdance someone to death if the quarters are very small and confined? No, and no.
In the end all that matters is that these guys are good at what they do, and they make no claims of any type of application or anything.