Hmmm -- I'ld question that motive for adding VG's on the aft fuselage.
Nope, had nothing to due with the APU. When the 737 originally entered service, the cabin crews started getting violently ill due to the vertical bounce in the tail (where the flight crew tends to spend a lot of their time). Apparently the separation of the aft fuselage airflow caused the oscillation at a frequency of a few hertz - which is very, very hard on the human body (the natural frequency of our insides is in that same frequency range - you can imagine what could happen when they match)
However if you look at the tail of a 787 near the APU exhaust, you'll see some strange additions - the result of failing the APU fluid leakage testing multiple times.