The variation is something the human ear doesn't notice when you solo the tracks. But when the four separate takes are summed together, they will not be identical in the "duplicate" sense. Instead, there's slight waveform and EQ (not in the effect EQ sense) differences constantly. You cannot emulate that by copypasting a single take, and it is not the same thing.
To put it very straightforward, it's the same thing as 1 person screaming something and then you copypaste that many times. Then you compare that to, for example, 10 people screaming the same thing. They will be just as loud by RMS when you level them to the same level, but the group of 10 screamers will sound a lot different than that one person.