It is true that PMK has more general stain than Pyrocat-HD (it depends on the film) but there assuredly is image-proportional stain. An article in a magazine (Darkroom Techniques?) a few years ago demonstrated this. You can bleach the silver image out of the negative and still print the image, using only the pyrogallol-produced stain.
I too have abandoned the after-bath. I think the after-bath tends to increase general stain moreso than image stain. I also have noticed no difficulty in attaining good stain after abandoning it, although I use an all-alkaline process which surely helps.
I stand corrected on Pyrocat-HD's longevity. I'll order some propylene glycol and make up a batch this way and see how it fares.