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
Yes, of course, that is a well known after the fact fix, that has endured until the Max came out. Speaks volumes on the design of the aircraft!
Now, about the other short term fixes that seem to have become permanent, like the tabs on top of the wing....or the vortex generators on the APU intakes....