Well... I can not find a single piece of information anywhere that supports your statement....

I can however find plenty that supports the description i gave earlier... Including pictures of the MD-80 cockpit where the word "Slats" are clearly seen on the flap-indicator and next to the flap-selector...
I'm quite sure that McDD knew what they put in their aircrafts, and i'm even more sure that the slats on the MD-80 are actuated mechanically, not aerodynamically...

And again: All wings can benefit from slats, not just near-supersonic wings... As i mentioned, the Aerospatiale/Socata Rallye has slats, and this is a out-of-production four-seat sport-aircraft with superb STOL-qualities....