It seems to be the phenomena that when the front glass is moved away from the other elements in the lens (as when you "close focus" or engage a "macro" mode), the aberrations normally corrected by the lens become uncorrected. In other words, these older lenses with "macro" modes tend to be average performers when outside the macro area, then have the "soft focus" look even when stopped down.
I don't know how/why companies sent lenses out the door which performed like that and why they allowed huge MACRO tags to be stamped in 4 places on every lens...someone had to say "wow, this doesn't look good at all"
It's the same with pretty much every 1980s "macro" lens I've owned, save the Soligor C/D 80-200 or something...that one is actually pretty good at close focus.