I can also confirm that '85 mixes were not done for TESB and ROTJ.

In completing GOUT syncs for the JSC and '92 Japanese fullscreen sets this week, I confirmed that they contain nearly identical soundtracks. Not digitally identical, but clearly the same mix, as they stay in nearly perfect sync over the course of the entire two films.

I have also compared with the original US fullscreen releases of Jedi (CLV, digital and analog tracks) and Empire (CAV, analog only) and can confirm that they are the same mix as well.