It says in the manual to adjust according to the set, so if it works, it works. I’ll not complain. I’ve just checked
Star Trek,
Moon and
Avatar and the soundtracks for each seem in sync with the picture.
What was confusing was that this particular setting is in the Video section of the PS3 settings, not the sound settings. Anyway, I now have full digital audio back, with DTS. I must not try to stop obsessing about this and enjoy watching HD films.