Does any one know why the actual configuration was selected?
Yes, because the routing of the highways was selected so that the most direct paths match the trips that people are taking, not to make a smooth path for the "through route" that happens follow the same route number.
More people are exiting to I-24 than are staying on I-75, so the configuration favors that.
2017 AADT figures:
I-75 directly north of interchange: 129,749
I-75 directly south of interchange: 108, 848
I-24 directly west of interchange: 134,737
Do the math and this gives us the following for each movement pair:
Between I-24 and I-75 to the north = 77,819
Between I-24 and I-75 to the south = 56,918
Thru traffic on I-75 = 51,930