Wake turbulence is a "thing" that trails an aircraft, and descends. If they had the same "footprint", the lower a/c would not see the WT - it would descend behind it. Besides, WT to two jumbo's is a flea in the wind... it is a BIG problem for C210's, however.
And the Airbus that crashed out of LGA Years ago was Flea Hit when it took off shortly after another did.