I don't know, but the time period that you are talking about roughly coincides with the advent of the one hour minilab. I'm not sure how they've adapted their chemistry in order to provide one hour service but I know that I can drop off a roll of color neg film at my local minilab and pick it up. processed only, in 10 minutes. I've processed plenty of C-41 by hand and machine and I know that you can't go dry to dry in 10 minutes in a standard process. The same process crunching would apply to a roll of 36 4"x6" prints. You must have to give up something for that kind of speed.

Combine that with the fact that many people with absolutely no photographic process control experience bought these machines as turnkey businesses and hired high school kids to run them and the drastic drop in quality and permanence seems inevitable.