"PF is caused by CA (
other explanations aren't very convincing, AFAIC) and is indeed an inherent problem in lens design."
I have no idea what is causing it,I don't buy into some of the hokey explanations that others ascribe to. Zeiss lenses are well known for doing it and they are supposedly designed to be relatively unscathed by such egregious lens design bloopers.
"An APO lens is characterised by the fact that it manages to focus three wavelengths at the same focal plane. For these three wavelengths it manages zero CA. I'd be surprised if that automatically had implications on OOF transitions (other than they are less colourful)."
That's exactly what i'm saying, the transition between the in focus and out of focus areas will be free of any colour fringing. The FA77 is a text book example of this type of fringing. the voigtlander 125mm f/2.5 APO Lanthar is a superb example of apochromatic correction.
"After I read your response, I don't get the drift of the post I replied to initially. You seem to be saying that you don't like lenses that inherently don't need the APO correction that longer lenses need? You don't like them because they don't have something (APO) that they don't need?"
I don't like it when a company labels a lens APO when it really isn't. It puts an unfair expectation on the performance of the lens(even if it is exceptional) and is more often than not used as an excuse to hike the price up - But these companies can basically do what the want, I'm just a consumer like everyone else.
I have nothing against apochromatic lenses, in fact; I wish someone would make a fast fifty apochromatic...that would irk leica photographer to no end. because it's optical aberrations would be largely cancelled out by the APO corrections and theoretically, the only resolution limiting factor to such a lens would be diffraction itself. I don't even want to know what a 50mm f/1.2 APO lens would cost though - seriously, I own a noctilux 50mm f/1.0 that is the most expensive 50mm lens I will ever own.
"I might be wrong but with PP CA correction, PF and other CA issues have become less of an issue so whether a lens is an APO lens or not seems less relevant than it used to be and other criteria (e.g., bokeh) can assume higher priority."
But the aberrations are still there - you can correct and image till the cows come home but it isn't going to look as good as an image taken with a lens that didn't have the same flaws. The differences
may be slight, but they are there.