If the rate of fire of a semi-automatic AK or AR rifle is about 120 rounds a minute versus whatever a fully-automatic version is, what difference does it make?
A HUGE difference. Try this: You have two rifles, one is a Mini-14 and the other is an AC556 (full-auto Mini). Each has a fully loaded 100 round Beta Mag attached. Using the full-auto you have 1 minute to hit intended targets and empty the magazine. Now, try hitting your targets and emptying 100 rounds in 1 minute with the semi-auto Mini-14.
I can tell you, full-auto in short bursts will be way more effective than trying to pull that trigger as fast as you can 100 times while trying to keep your muzzle on target. It's not even close to being the same.