Your comment on the AA 787-900 is incorrect as PE pax can still use the lavatories in front of the PE bulkhead row but they have to access them through each aisle; the dividing curtain on both aisles is located in front of these two lavs so J pax would have to cross over into PE to use the two lavs by doors 2L/2R. AA did this to prevent PE pax from going into the middle galley where there are usually snacks for J.

I don't know why (I'm guessing due to complaints) but if you look carefully, there was an extra set of curtains between J and PE which previously allowed the lavatories by doors 2L/2R to be exclusive for J, but AA removed these curtains and nothing prevents PE pax from using the lavs now; however, if anyone tries to go through the galley/bar area, the crew will tell you that's only for J though you can use the 2L/2R lavatories as long as you aren't trying to cross onto the other side through the mid galley.